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Plant protection and growth stimulation by microorganisms:biotechnological applications of Bacilli in agricultureAlejandro Perez-Garcıa, Diego Romero and Antonio de Vicente

The increasing demand for a steady, healthy food supply

requires an efficient control of the major pests and plant

diseases. Current management practices are based largely on

the application of synthetic pesticides. The excessive use of

agrochemicals has caused serious environmental and health

problems. Therefore, there is a growing demand for new and

safer methods to replace or at least supplement the existing

control strategies. Biological control, that is, the use of natural

antagonists to combat pests or plant diseases has emerged as

a promising alternative to chemical pesticides. The Bacilli offer

a number of advantages for their application in agricultural

biotechnology. Several Bacillus-based products have been

marketed as microbial pesticides, fungicides or fertilisers.

Bacillus-based biopesticides are widely used in conventional

agriculture, by contrast, implementation of Bacillus-based

biofungicides and biofertilizers is still a pending issue.

Address

Departamento de Microbiologıa, Facultad de Ciencias, Universidad de

Malaga, Instituto de Hortofruticultura Subtropical y Mediterranea,

Boulevard Louis Pateur-Campus Universitario de Teatinos s/n, 29071

Malaga, Spain

Corresponding author: Perez-Garcıa, Alejandro ([email protected])

Current Opinion in Biotechnology 2011, 22:1–7

This review comes from a themed issue on

Food biotechnology

Edited by Oscar Kuipers and Tjakko Abee

0958-1669/$ – see front matter

# 2010 Elsevier Ltd. All rights reserved.

DOI 10.1016/j.copbio.2010.12.003

IntroductionInsects and fungi affecting crops and post-harvested

fruits and vegetables are major threats to food production.

They have led to important economic losses worldwide,

particularly over the past few decades as agricultural

production has intensified. To face these problems, pro-

ducers have become increasingly dependent on agro-

chemicals. However, intensive use of these compounds

in conventional crop management has led to the emer-

gence of frequent problems of pesticide resistance in

insect pests and microbial pathogens and has also caused

serious problems affecting not only human health but also

the quality of the environment. Therefore, there is an

increasing demand by growers and consumers for new

Please cite this article in press as: Perez-Garcıa A, et al. Plant protection and growth stimulation by

(2011), doi:10.1016/j.copbio.2010.12.003

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environmentally friendly methods to replace, or at least

supplement, the existing chemical-based strategies

thereby achieving safer and more effective pest and

disease control.

Biological control, that is, the use of natural antagonistic

organisms to combat pests or suppress plant diseases,

offers an interesting alternative to the use of chemicals

[1�,2�]. Some aerobic spore-forming bacteria possess sev-

eral advantages that make them good candidates for use

as biological control agents. Firstly, some of these bacteria

produce several different types of insecticidal and anti-

microbial compounds. Secondly, they induce growth and

defence responses in the host plant. Furthermore, Bacillusspecies are able to produce spores that allow them to resist

adverse environmental conditions and permit easy for-

mulation and storage of the commercial products [3,4].

Members of the genus Bacillus are among the beneficial

bacteria exploited as microbial pesticides, fungicides or

fertilizers. Bacillus-based products represent the most

important class of microbial products for phytosanitary

use commercially available [5,6]. In this article, we pro-

vide a short overview about the current biotechnological

applications of bacilli in agriculture (Figure 1), and we

discuss the potential of these microorganisms for promot-

ing plant health in 21st century agriculture.

Bacillus thuringiensis, the first biopesticideSince its discovery in 1901 as a microbial insecticide,

Bacillus thuringiensis has been widely used to control insect

pests important in agriculture, forestry and medicine. Its

principal characteristic is the synthesis, during sporulation,

of a crystalline inclusion containing proteins known as d-

endotoxins or Cry proteins, which have insecticidal proper-

ties. To date, over one hundred B. thuringiensis-based

bioinsecticides have been developed, which are mostly

used against lepidopteran, dipteran and coleopteran larvae.

In addition, the genes that code for the insecticidal crystal

proteins have been successfully transferred into different

crops plants, which has led to significant economic benefits.

Because of their high specificity and their safety in the

environment, B. thuringiensis and Cry proteins are efficient,

safe and sustainable alternatives to chemical pesticides for

the control of insect pests [7��,8].

The toxicity of the Cry proteins have traditionally been

explained by the formation of transmembrane pores or ion

channels that lead to osmotic cell lysis [7��]. In a recent

study, a more precise trimeric building block model for

Cry toxins ion channel formation has been proposed

microorganisms: biotechnological applications of Bacilli in agriculture, Curr Opin Biotechnol


http://dx.doi.org/10.1016/j.copbio.2010.12.003

mailto:[email protected]


2 Food biotechnology


Figure 1

Biofertilizers

Bacillus

Biofungicides

Bio

pest

icid

es

Current Opinion in Biotechnology

The bacilli target triangle. Current agricultural usage of Bacillus-based

products as microbial pesticides, fungicides, and stimulators of plant

growth. Although some Bacillus species also display bactericidal and

nematicidal abilities, these features have not been specifically exploited

yet or their implementation is very limited.

based on sequence conservation and mutagenesis data

[9]. In addition to this, Cry toxin monomers also seem to

promote cell death in insect cells through a mechanism

involving an adenylyl cyclase/PKA signalling pathway

[10]. However, despite this entomopathogenic potential,

controversy has arisen regarding the pathogenic lifestyle


(2011), doi:10.1016/j.copbio.2010.12.003

Table 1

Some commercial formulations of Bacillus-based biofungicides.

Trade name Bacillus species Target pathogen/disease

Avogreen B. subtilis Cercospora spot

Ballad Plus B. pumilus Rust, powdery mildew,

cercospora, brown spot

Biobest B. subtilis Sheath blight, blast, brown spo

Companion B. subtilis Rhizoctonia, Pythium, Fusarium

Phytophthora, Sclerotinia

EcoGuard B. licheniformis Dollar spot, anthracnose

HiSticka B. subtilis Fusarium, Rhizoctonia, Asperg

Kodiak B. subtilis Rhizoctonia, Fusarium,

Pythium Aspergillus

Larminar B. subtilis Alternaria, Botryodiplodia,

Colletotrichum, Corticium,

Fusarium, Phytophthora

Rhapsody B. subtilis Rhizoctonia, Fusarium,

Pythium, Phytophthora

Serenade B. subtilis Rusts, powdery mildews, Botry

Sclerotinia

Sonata B. pumilus Rusts, powdery and downy mi

Subtilex B. subtilis Rhizoctonia, Fusarium, Asperg

Taegro B. amyloliquefaciens Rhizoctonia, Fusarium

a This formulation is composed by B. subtlis and rhizobial cells.


of B. thuringiensis. Recent reports claim that B. thuringiensisrequires the co-operation of commensal bacteria within

the insect gut to be fully pathogenic [11,12]. In clear

opposition, genomic and proteomic studies have been

argued as the most solid data to convincingly demonstrate

that B. thuringiensis is a primary pathogen rather than a

soil-dwelling saprophyte [13,14,15�]. In any case, what is

certainly not doubtful is that B. thuringiensis is one of the

most successful examples of the use of microorganisms in

agricultural biotechnology, with about 70% of the global

biopesticide market involving products based on B. thur-ingiensis [16], and will continue to be one of the most

important microbial weapons to defend our crops from

insect pests.

Bacilli as biofungicidesBesides the insecticidal properties of B. thuringiensis, some

bacilli display other characteristics that may directly or

indirectly contribute to crop productivity. Members of the

genus Bacillus are often considered as microbial factories

for the production of a vast array of biologically active

molecules, some of which are potentially inhibitory for

fungal growth [3]. Plant pathogenic fungi and oomycetes

are major threats for crops and plant production. Therefore,

the control of fungal diseases by bacilli represents another

interesting opportunity for agricultural biotechnology.

Indeed, several commercial products based on various

Bacillus species such as B. amyloliquefaciens, B. licheniformis,B. pumilus and B. subtilis have been marketed as biofungi-

cides (Table 1) [6]. These Bacillus-based products have

been developed especially for the control of fungal diseases


Crop Manufacturer

Avocado Stimuplant, South Africa

Soybean AgraQuest, USA

t Rice Appliedchem, Thailand

, Greenhouse, nursery

and ornamental crops

Growth Products,USA

Turf Novozymes, Denmark

illus Soybean and peanuts Becker Underwood, USA

Cotton, legumes, soybean

and vegetable crops

Bayer CropScience, USA

Vegetables, fruit trees,

ornamentals, rice, and

field crops

Appliedchem, Thailand

Turf and ornamental,

vegetable and fruit

greenhouse crops

AgraQuest, USA

tis, Vegetable, wine,

nut and fruit crops

AgraQuest, USA

ldews Vegetable and fruit crops AgraQuest, USA

illus Field, ornamental and

vegetable crops

Becker Underwood, USA

Tree seedlings, ornamentals

and shrubs

Novozymes, Denmark



Plant protection and growth stimulation by microorganisms Perez-Garcıa, Romero and de Vicente 3


in three main environments: soil, greenhouses and post-

harvest. These situations offer the best conditions for

optimal disease suppression activity because biological

control agents require specific environmental conditions

such as high relative humidity [6].

A high number of reports have described the beneficial

effects of several Bacillus species against diseases elicited

by oomycetes and fungal pathogens. Some examples are

the suppression of root diseases (such as avocado root rot,

tomato damping-off and wheat take-all), foliar diseases

(such as cucurbit and strawberry powdery mildews) and

postharvest diseases (such as green, grey and blue

moulds) [17–19,20�,21–24]. However, the implementa-

tion in conventional agriculture of these Bacillus-based

products is still a pending issue. Most of these reports

highlight the need to integrate these Bacillus agents

mainly with fungicides to optimise disease management

[21,24,25,26]. Unfortunately, very little work has been

done on their integration with other management tools

such as cultural practises, host resistance, natural products

and other biological control agents. The research progress

made in the use of bacilli as biofungicides during the past


(2011), doi:10.1016/j.copbio.2010.12.003

Figure 2

iturin A

fengycin

H

H

HH

H H

HHH

HH

H

H H

HH

H

H

HH

HHH

H H

H

HH

H

HH

H

H

H

HH

H

HH

H

O

O

O

O

O

OOO

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

OO

OO

O

OOOO

O

O

NN

N

N

N

N

N

N

NN

NN

NN

NN

N

N

N

N

N

N

N

N

2D chemical structures of representative members of the three lipopeptide fa

and surfactins (surfactin). Nitrogen and oxygen atoms are depicted in blue a

PubChem (http://pubchem.ncbi.nlm.nih.gov/).


two decades has been remarkable; if this pace continues,

the use of Bacillus-based products to combat fungal dis-

eases will be greatly expanded in the future.

Bacillus lipopeptides, key molecules forbiological control of plant diseasesAntagonism to pathogens is the main mechanism of bio-

control that has been exploited to combat plant diseases

with Bacillus species. Cell wall-degrading enzymes (such as

chitinases, glucanases and proteases), peptide antibiotics

and other small molecules (such as volatile organic com-

pounds) are secreted by various species, and many of these

have been shown to contribute to pathogen suppression

[27]. Lipopeptides are among the antibiotic compounds

most frequently produced by Bacillus species and the

Bacillus compounds more extensively studied. These are

amphiphilic compounds that share a common structure

consisting of a lipid tail linked to a short cyclic oligopeptide.

Lipopeptides are classified into three families depending

on their amino acid sequence: iturins, fengycins and sur-

factins (Figure 2) [28��]. The surfactins are powerful

biosurfactants, which show antibacterial activity but no

marked fungitoxicity (with some exceptions) [29]. The


surfactin

H

H

H

H

H

H

HH

HH

HH

O OO

O

O

O

O

OOO

O

O

O

N

N

N N

N

N

N


milies produced by Bacillus species, iturins (iturin A), fengycins (fengycin)

nd red, respectively. The 2D chemical structures were taken from



http://pubchem.ncbi.nlm.nih.gov/



iturins display strong antifungal action against a wide

variety of yeasts and fungi but only limited antibacterial

activity. Fengycins also show a strong fungitoxic activity,

specifically against filamentous fungi [28��]. The ability of

various Bacillus strains to control fungal soilborne, foliar

and postharvest diseases has been attributed mostly to

iturins and fengycins [28��,30�,31]. The amphiphilic struc-

ture of lipopeptides allows them to interact with biological

membranes and induce the formation of pores. Such altera-

tions of plasma membrane integrity promote internal

osmotic imbalance and widespread disorganisation of cyto-

plasm in fungal cells [32�]. Interestingly, iturins have also

been involved in the biological control ability of B. subtilisstrains against gram-negative phytopathogenic bacteria (H

Zeriouh et al., unpublished), thus expanding the range of

plant diseases that could be potentially controlled by bacilli

(Figure 3).

Besides antibiosis, lipopeptides may have additional

roles in biocontrol. Selected strains of Bacillus and other

plant growth-promoting rhizobacteria (PGPR) can sup-

press plant diseases caused by both root and foliar patho-

gens, by inducing a resistance response in the host plant

designated as ‘induced systemic resistance’ or ISR [33�].Surfactin and fengycin lipopeptides have recently been

identified as bacterial determinants responsible for eli-

citation of ISR in the host plant [34�]. It is yet unclear


(2011), doi:10.1016/j.copbio.2010.12.003

Figure 3

antibacterials motility andbiofilm formation

elicitors forISR activation

antifungals

fen, itu

itu

srf

Bacillus

fen, srf


Main roles of Bacillus lipopeptides regarding the biological control of

plant diseases by bacilli. Fengycin and iturin lipopeptides have been

widely characterised as antifungal compounds against several

phytopathogenic fungi and oomycetes. Iturins may also have additional

antibacterial potential at least against some Gram-negative plant

pathogenic bacteria. Fengycin and surfactin lipopeptides seem to act as

elicitors for activation of induced systemic resistance (ISR) in the roots of

the host plant, leading to suppression or reduction of plant diseases

caused by soil-borne and air-borne plant pathogens. Surfactin

lipopeptides are essential for motility. Surfactin acts as a signalling

molecule for biofilm formation and also seems to be required for

colonisation of root and leaf surfaces by plant-associated bacilli.

Abbreviations are: fen, fengycin lipopeptides; itu, iturin lipopeptides; and

srf, surfactin lipopeptides.


whether the induction of the ISR response by lipopep-

tides requires specific receptors in the plant membrane.

It is postulated that some lipopeptides may induce a

disturbance or transient channelling in the plasma mem-

brane, which in turn activates a cascade of molecular

events leading to enhanced defence [35�]. Nevertheless,

these findings open up a new area of research to further

exploit these potential beneficial effects of bacilli and

especially to gain more insight on the key structural

features and constituents of lipopeptides involved in

the induction of plant defence responses [36�].

The efficient protection of plants by biocontrol agents

requires their proper establishment in the host plant.

Chemotaxis, motility and growth are essential players

in this process. Lipopeptides can also influence the eco-

logical fitness of the producing strain contributing to plant

colonisation and persistence in the plant environment.

Thus, surfactin seems to be essential for swarming moti-

lity in B. subtilis [37]. In planta, the secretion of surfactin

and the formation of a stable, extensive biofilm that

occurs upon root colonisation by B. subtilis has been

shown to be crucial for disease suppression [38]. Similar

results have been obtained with surfactin-deficient

mutants of B. subtilis, which show disorganised biofilm

formation and reduced biocontrol ability of fungal and

bacterial diseases after application on leaves (H Zeriouh

et al., unpublished). Moreover, a recent study attributes to

surfactin the role of triggering signal molecule for extra-

cellular matrix formation in functional and robust biofilms

of B. subtilis [39�]. The lack of knowledge on many of

these crucial aspects of Bacillus ecology should stimulate

more intensive research. In this sense, the isolation of

Bacillus strains with enhanced colonisation capabilities

could be another strategy to improve the performance of

bacilli-based fungicides. Nevertheless, the attempts pub-

lished so far following this strategy have resulted in the

isolation of a remarkable low percentage of endospore

formers, suggesting that Bacillus species are poor com-

petitive colonizers at least for roots [40,41].

Bacilli as biofertilisersAnother interesting and well-documented ability of bacilli

is their capacity to promote plant health by stimulating

nutrition and growth. The mechanisms used by Bacillusspecies to achieve this are biofertilisation and direct plant

growth promotion. In many soils, essential mineral nutri-

ents such as inorganic phosphate and ferric iron ions are

largely unavailable to plants because they are fixed in

insoluble forms. Through biofertilisation, Bacillus popu-

lations improve the bioavailability of essential compounds

and increase the supply of mineral nutrients to the host

plant. In soil, organic phosphorus is stored mainly as

insoluble myo-inositol hexaphosphate or phytate. Several

Bacillus species, such as B. amyloliquefaciens, contribute to

soil biofertilisation through the production of extracellular

phytases, which are special phosphatases that catalyse the






sequential hydrolysis of phytate to less-phosphorylated

myo-inositol derivatives and inorganic phosphate [42�].In addition, phytases eliminate chelate-forming phytate,

which is known to bind nutritionally important minerals

(such as Zn2+, Fe2+, Ca2+). Something similar happens to

iron. In the soil, the most prevalent form of iron is Fe3+,

which is relatively insoluble compared with the more

reduced form Fe2+ and less readily taken up by plants

and microorganisms. Bacillus species, such as B. megaterium,

can reduce metals, potentially increasing the bioavailabil-

ity of iron [43].

Direct plant growth promotion by Bacillus involves the

modulation of plant development through the production

of phytohormones [44]. Thus, several Bacillus species are

capable of producing auxin that might stimulate root

proliferation and nutrient uptake [45]. For example, in

B. amyloliquefaciens the biosynthesis of indole-3-acetic

acid (IAA) is responsible for plant growth promotion,

which in turn is strictly dependent on the presence of

tryptophan, one of the main compounds present in plant

root exudates [46]. Similarly, the inoculation of plants

with cytokinin-producing B. subtilis or B. megateriumstrains has a beneficial effect on plant growth [47,48�].In B. pumilus, however, plant growth promotion has been

associated with production of either gibberellin or ABA

and jasmonic acid [49,50]. Finally, volatile organic com-

pounds from B. subtilis have been shown to trigger growth

promotion in Arabidopsis by regulating auxin homeostasis,

thus providing a new paradigm as to how these bacteria

promote plant growth [51�]. For all of these reasons,

various Bacillus-based products have been launched to

the market under the category of biofertilisers. Further

research on this topic will help to accelerate the devel-

opment and application of new products that improve

crop quality and yields.

Conclusions and perspectivesThe need for a continuous supply of food has led conven-

tional agriculture to be strongly dependent on chemicals.

The increasing concern of consumers and governments on

food safety has led growers to explore new environmentally

friendly methods to replace, or at least supplement, the

current chemical-based practices. During the past few

decades, research on agricultural applications of aerobic

endospore-forming bacteria has conducted to the devel-

opment of a variety of Bacillus-based products exploiting

their insecticidal, antifungal and fertilising properties. The

molecular and physiological mechanisms by which Bacillusspecies exert these beneficial activities are not completely

understood in many cases. Nevertheless, bacilli may have

additional applications. Some Bacillus species have shown

an ability to control plant-parasitic nematodes. The mech-

anisms by which bacilli reduce nematode population and

root infestation are not completely elucidated. The pro-

duction of cuticle-degrading proteases as well as Cry toxins

seems to be responsible for toxicity of Brevibacillus later-


(2011), doi:10.1016/j.copbio.2010.12.003


osporus and B. thuringienis, respectively. In other species

such as B. amyloliquefaciens and B. firmus beneficial effect is

believed to be achieved through ISR elicitation [52�].There are a few commercial Bacillus-based bionematicidal

formulations but their implementation is still very limited.

Furthermore, novel functions of bacilli such as quorum

quenching have been demonstrated to restrain bacterial

infections. Many bacterial pathogens have evolved cell–cell communication (quorum-sensing) mechanisms to

regulate expression of virulence factors. Key components

in these regulation systems are N-acyl homoserine lactones

(AHLs), which act as signal molecules. Some Bacillusspecies such as B. thuringiensis are able to break down

AHLs (quorum quenching) by production of N-acyl homo-

serine lactone lactonases, which open the lactone ring of

AHLs, significantly silencing bacterial virulence [53�].Therefore, exploitation of these activities could expand

the phytoprotection possibilities of bacilli also as microbial

bactericides.

Bacillus-based products have great potential for use in

integrated pest management (IPM) systems; unfortu-

nately, relatively little work has been undertaken on their

integration with other IPM tools such as cultural prac-

tices, host resistance, chemical control, and other bio-

logical control agents. Formulation and application

methods are key issues influencing the efficacy of com-

mercial products [54�]; research on these topics should be

focused on overcoming environmental restrictions, which

are the main reasons for failure or lack of consistence of

biological control agents in the field. Genetic engineering

may provide a useful tool for the enhancement of per-

formance although genetically engineered microbes are

not yet allowed to enter the market. Finally, as whole

genome sequences become available for Bacillus species

of commercial interest [55��], high-throughput studies

can be undertaken to gain knowledge about the biocon-

trol competence of these agents. As new progress on these

topics is made, new and better Bacillus-based formu-

lations will be developed. Therefore, we anticipate a

more relevant role for these microorganisms in promoting

plant health in the 21st century agriculture.

AcknowledgementsThe authors gratefully acknowledge past and ongoing support for their workon the use of bacilli as biocontrol agents from Plan Nacional de I + D + I ofthe Ministerio de Ciencia e Innovacion, Spain (AGL2001-1837; AGL2004-0656; AGL2007-65340; AGL2010-21848), co-financed with FEDER funds(European Union).

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� of special interest

�� of outstanding interest

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20.�

Romero D, de Vicente A, Zeriouh H, Cazorla FM, Fernandez-Ortuno D, Tores JA, Perez-Garcıa A: Evaluation of biologicalcontrol agents for managing cucurbit powdery mildew ongreenhouse-grown melon. Plant Pathol 2007, 56:976-986.

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21. Pertot I, Zasso R, Amsalem L, Baldessari M, Angeli G, Elad Y:Integrating biocontrol agents in strawberry powdery mildewcontrol strategies in high tunnel growing system. Crop Prot2008, 27:622-631.

22. Leelasuphakul W, Hemmanee P, Chuenchitt S: Growth inhibitoryproperties of Bacillus subtilis strains and their metabolitesagainst the green mold pathogen (Penicillium digitatum Sacc.)of citrus fruit. Postharvest Biol Technol 2008, 48:113-121.

23. Jamalizadeh M, Etebarian HR, Alizadeh A, Aminian H: Biologicalcontrol of gray mold of apple fruits by Bacillus licheniformis(EN74-1). Phytoparasitica 2008, 36:23-29.

24. Arrebola E, Sivakumar D, Bacigalupo R, Korsten L: Combinedapplication of antagonist Bacillus amyloliquefaciens andessential oils for the control of peach postharvest diseases.Crop Prot 2010, 29:369-377.

25. Nofal MA, Haggag WM: Integrated management of powderymildew of mango in Egypt. Crop Prot 2006, 25:480-486.

26. Correa OS, Montecchina MS, Berti MF, Fernandez Ferrari MC,Pucheu NL, Kerber NL, Garcia AF: Bacillus amyloliquefaciensBNM122 a potential microbial biocontrol agent applied onsoybean seeds, cause a minor impact on rhizosphereand soil microbial communities. Appl Soil Ecol 2009,41:185-194.

27. Shoda M: Bacterial control of plant diseases. J Biosci Bioeng2000, 89:515-521.

28.��

Ongena M, Jacques P: Bacillus lipopeptides: versatile weaponsfor plant disease biocontrol. Trends Microbiol 2008,16:115-125.

In an excellent overview of the role of Bacillus lipopeptides in thebiological control of plant diseases, the authors show how the differentstructural traits and physico-chemical properties of these effective sur-face-active and membrane-active amphiphilic biomolecules may explaintheir involvement in most of the mechanisms developed by Bacillus for thebiocontrol of different plant pathogens.

29. Tendulkar SR, Saikumari YK, Patel V, Raghotama S, Munshi TK,Balaram P, Chattoo BB: Isolation, purification andcharacterization of an antifungal molecule produced byBacillus licheniformis BC98, and its effect on phytopathogenMagnaporthe grisea. J Appl Microbiol 2007, 103:2331-2339.

30.�

Romero D, de Vicente A, Rakotoaly RH, Dufour SE, Veening J-W,Arrebola E, Cazorla FM, Kuipers OP, Paquot M, Perez-Garcıa A:The iturin and fengycin families of lipopeptides are key factorsin antagonism of Bacillus subtilis toward Podosphaera fusca.Mol Plant-Microbe Interact 2007, 20:430-440.

This work is an elegant examination of the role of iturin and fengycinlipopeptides as the main mechanism of biocontrol of two strains of B.subtilis against the cucurbit powdery mildew fungus P. fusca.

31. Arrebola E, Jacobs R, Korsten L: Iturin A is the principal inhibitorin the biocontrol activity of Bacillus amyloliquefaciensPPCB004 against postharvest fungal pathogens. J ApplMicrobiol 2010, 108:386-395.

32.�

Romero D, de Vicente A, Olmos JL, Davila JC, Perez-Garcıa A:Effect of lipopeptides of antagonistic strains of Bacillussubtilis on the morphology and ultrastructure of the cucurbitfungal pathogen Podosphaera fusca. J Appl Microbiol 2007,103:969-976.






The authors describe the negative effects of lipopeptides from B. subtilison growth and development of the fungal pathogen P. fusca by differentmicroscopic approaches.

33.�

Choudhary DK, Johri BN: Interactions of Bacillus spp. andplants—with special reference to induced systemic resistance(ISR). Microbiol Res 2009, 164:493-513.

Updated review on Bacillus spp. as biological control agents of plantdiseases. Special attention is paid to the elicitation of induced systemicresistance (ISR) as a mechanism of plant protection against bioticstresses.

34.�

Ongena M, Jourdan E, Adam A, Paquot M, Brans A, Joris B,Arpigny JL, Thonart P: Surfactin and fengycin lipopeptides ofBacillus subtilis as elicitors of induced systemic resistance inplants. Environ Microbiol 2007, 9:1084-1090.

This study identifies, for the first time, surfactin and fengycin lipopeptidesas bacterial determinants responsible for the elicitation of induced sys-temic resistance (ISR) by plant-associated Bacillus.

35.�

Jourdan E, Henry G, Duby F, Dommes J, Barthelemy JP,Thonart P, Ongena M: Insights into the defense-related eventsoccurring in plant cells following perception of surfactin-typelipopeptide from Bacillus subtilis. Mol Plant Microbe Interact2009, 22:456-468.

The present study sheds new light on defence-related events inducedfollowing plant cell recognition of amphiphilic lipopeptides from B. subtilisand more globally on the way elicitors from beneficial bacteria can beperceived by host plant cells.

36.�

Raaijmakers JM, de Bruijn I, Nybroe O, Ongena M: Naturalfunctions of lipopeptides from Bacillus and Pseudomonas:more than surfactants and antibiotics. FEMS Microbiol Rev2010, 34:1037-1062.

This review gives a detailed overview of the versatile functions of lipo-peptides in the biology of Pseudomonas and Bacillus species, andhighlights their role in competitive interactions with coexisting organisms,including bacteria, fungi, oomycetes, protozoa, nematodes and plants.

37. Julkowska D, Obuchowski M, Holland IB, Seror SJ: Comparativeanalysis of the development of swarming communities ofBacillus subtilis 168 and a natural wild type: critical effects ofsurfactin and the composition of the medium. J Bacteriol 2005,187:65-76.

38. Bais HP, Fall R, Vivanco JM: Biocontrol of Bacillus subtilisagainst infection of Arabidopsis roots by Pseudomonassyringae is facilitated by biofilm formation and surfactinproduction. Plant Physiol 2004, 134:307-319.

39.�

Lopez D, Vlamakis H, Losick R, Kolter R: Cannibalism enhancesbiofilm development in Bacillus subtilis. Mol Microbiol 2009,74:609-618.

The authors describe a novel function for surfactin lipopeptides as atriggering signal for cannibalism, a mechanism to delay sporulation, andmatrix production, both processes leading to biofilm formation in B.subtilis.

40. Pliego C, Cazorla FM, Gonzalez-Sanchez MA, Perez-Jimenez RM,de Vicente A, Ramos C: Selection for biocontrol bacteriaantagonistic toward Rosellinia necatrix by enrichment ofcompetitive avocado root tip colonizers. Res Microbiol 2007,158:463-470.

41. Validov S, Kamilova F, Qi S, Stephan D, Wang JJ, Makarova N,Lugtenberg B: Selection of bacteria able to control Fusariumoxysporum f. sp. radicis-lycopersici in stonewool substrate. JAppl Microbiol 2007, 102:461-471.

42.�

Jorquera M, Martınez O, Muruyama F, Marschner P, de la LuzMora M: Current and future biotechnological applications ofbacterial phytases and phytase-producing bacteria. MicrobesEnviron 2008, 23:182-191.

Comprehensive review on the current knowledge of bacterial phytasesand phytase-producing bacteria, as well as their potential biotechnolo-gical applications, including new fields that are poorly explored, such asfish nutrition, environmental protection and plant nutrition.

43. Valencia-Cantero E, Hernandez-Calderon E, Velazquez-Becerra C, Lopez-Meza JE, Alfaro-Cuevas R, Lopez-Bucio J: Roleof dissimilatory fermentative iron-reducing bacteria in Feuptake by common bean (Phaseolus vulgaris L.) plants grownin alkaline soil. Plant Soil 2007, 291:263-273.


(2011), doi:10.1016/j.copbio.2010.12.003


44. Tsavkelova EA, Klimova SY, Cherdyntseva TA, Netrusov AI:Microbial producers of plant growth stimulators and theirpractical use: a review. Appl Biochem Microbiol 2006,42:117-126.

45. Spaepen S, Vanderleyden J, Remans R: Indole-3-acetic acid inmicrobial and microorganism-plant signaling. FEMS MicrobiolRev 2007, 31:425-448.

46. Idris EE, Iglesias DJ, Talon M, Borriss R: Tryptophan-dependentproduction of indole-3-acetic acid (IAA) affects level of plantgrowth promotion by Bacillus amyloliquefaciens FZB42. MolPlant-Microbe Interact 2007, 20:619-626.

47. Arkhipova TN, Prinsen E, Veselov SU, Martinenko EV, Melentiev AI,Kudoyarova GR: Cytokinin producing bacteria enhance plantgrowth in drying soil. Plant Soil 2007, 292:305-315.

48.�

Ortız-Castro R, Valencia-Cantero E, Lopez-Bucio J: Plant growthpromotion by Bacillus megaterium involves cytokininsignaling. Plant Signal Behav 2008, 3:263-265.

In this work the role of cytokinin signalling in mediating plant growthpromotion in response to B. megaterium inoculation was investigatedusing A. thaliana mutants lacking one, two or three of the putativecytokinin receptors and one gene involved in cytokinin signalling.

49. Joo G-J, Kim Y-M, Kim J-T, Rhee I-K, Kim J-H, Lee I-J:Gibberellins-producing rhizobacteria increase endogenousgibberellins content and promote growth of red peppers. JMicrobiol 2005, 43:510-515.

50. Forchetti G, Masciarelli O, Alemano S, Alvarez D, Abdala G:Endophytic bacteria in sunflower (Helianthus annuus L.):isolation, characterization, and production of jasmonates andabscisic acid in culture medium. Appl Microbiol Biotechnol2007, 76:1145-1152.

51.�

Zhang H, Kim MS, Krishnamachari V, Payton P, Sun Y, Grimson M,Farag MA, Ryu CM, Allen R, Melo IS, Pare PW: Rhizobacterialvolatile emissions regulate auxin homeostasis and cellexpansion in Arabidopsis. Planta 2007, 226:839-851.

The authors show for the first time how volatile organic acids from B.subtilis are able to regulate auxin homeostasis and cell expansion inArabidopsis, providing a new paradigm as to how rhizobacteria promoteplant growth.

52.�

Tian B, Yang J, Zhang K-Q: Bacteria used in the biologicalcontrol of plant-parasitic nematodes: populations,mechanisms of action, and future prospects. FEMS MicrobiolEcol 2007, 61:197-213.

This review details the nematophagous bacteria known to date andfocuses on recent research developments concerning their pathogenicmechanisms at the biochemical and molecular levels. The authors alsoreview a number of molecular biological approaches currently used in thestudy of bacterial pathogenesis in nematodes.

53.�

Zhou Y, Choi Y-L, Sun M, Yu Z: Novel roles of Bacillusthuringiensis to control of plant diseases. Appl MicrobiolBiotechnol 2008, 80:563-572.

This review shows novel potential applications of Bacillus species in thecontrol of plant diseases, using, for example, a new strategy to suppressplant bacterial diseases by quenching bacterial quorum sensing. N-acylhomoserine lactone lactonase produced by B. thuringiensis can open thelactone ring of N-acyl homoserine lactone, a signal molecule in thebacterial quorum-sensing system, significantly silencing bacterial viru-lence.

54.�

Sorokulova IB, Krumnow AA, Pathirana S, Mandell AJ,Vodyanoy V: Novel methods for storage stability and release ofBacillus spores. Biotechnol Prog 2008, 24:1147-1153.

This work illustrates the development of new formulations that increasethe shelf life of Bacillus spores.

55.��

Chen XH, Koumoutsi A, Scholz R, Schneider K, Vater J,Sussmuth R, Piel J, Borriss R: Genome analysis of Bacillusamyloliquefaciens FZB42 reveals its potential for biocontrol ofplant pathogens. J Biotechnol 2009, 140:27-37.

This work shows a detailed analysis of the first genome of a Bacillus strainwith demonstrated ability of controlling plant pathogens. In total, FZB42dedicates about 340 kb, corresponding to 8.5% of its total geneticcapacity, to the synthesis of secondary metabolites such as lipopeptidesand polyketides with antifungal, antibacterial and nematocidal activity.




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