algae and fungi

8/7/2019 Algae and fungi

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Algae

From Wikipedia, the free encyclopedia

Jump to: navigation, searchFor other uses, see Algae (disambiguation) and Alga (disambiguation).

Algae

Laurencia, a marine genus of Red Algae from Hawaii.

Scientific classification

Domain: Eukaryota

Included groups

y Archaeplastida

o Chlorophyta (Green algae)o Rhodophyta (Red algae)

o Glaucophytay Rhizaria, Excavata

o Chlorarachniophyteso Euglenids

y Chromista, Alveolatao Heterokonts

Bacillariophyceae (Diatoms) Axodine

Bolidomonas Eustigmatophyceae

Phaeophyceae (Brown algae) Chrysophyceae (Golden algae)

Raphidophyceae Synurophyceae

Xanthophyceae (Yellow-green algae)o Cryptophyta

o Dinoflagellates


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o Haptophyta

Excluded groups

y Cyanobacteriay Plantae

The lineage of algae according to Thomas Cavalier-Smith. The exact number and placement of

endosymbiotic events is not yet clear, so this diagram can be taken only as a general guide[1][2]

Itrepresents the most parsimonious way of explaining the three types of endosymbiotic origins of

plastids. These types include the endosymbiotic events of cyanobacteria, red algae and greenalgae, leading to the hypothesis of the supergroups Archaeplastida, Chromalveolata and Cabozoa

respectively. However, the monophyly ofCabozoa has been refuted and the monophylies ofArchaeplastida and Chromalveolata are currently strongly challenged. Endosymbiotic events are

noted by dotted lines.

Algae (singularalga /l/, Latin for "seaweed") are a large and diverse group of simple,

typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and

most complex marine forms are called seaweeds. They are photosynthetic, like plants, and"simple" because they lack the many distinct organs found in land plants.

Though the prokaryotic Cyanobacteria (commonly referred to as blue-green algae) were

traditionally included as "algae" in older textbooks, many modern sources regard this asoutdated

[3]as they are now considered to be closely related to bacteria.

[4]The term algae is now

restricted to eukaryotic organisms.[5]

All true algae therefore have a nucleus enclosed within amembrane and plastids bound in one or more membranes.

[3][6]Algae constitute a paraphyletic

and polyphyletic group,[3]

as they do not include all the descendants of the last universal ancestornor do they all descend from a common algal ancestor, although their plastids seem to have a

single origin.[1]

Diatoms are also examples of algae.


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Algae lack the various structures that characterize land plants, such as phyllids (leaves)and rhizoids in nonvascular plants, or leaves, roots, and other organs that are found in

tracheophytes (vascular plants). Many are photoautotrophic, although some groups containmembers that are mixotrophic, deriving energy both from photosynthesis and uptake of organic

carbon either by osmotrophy, myzotrophy, or phagotrophy. Some unicellular species rely

entirely on external energy sources and have limited or no photosynthetic apparatus.

Nearly all algae have photosynthetic machinery ultimately derived from the Cyanobacteria, and

so produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria suchas purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have

been dated back to 1.6 to 1.7 billion years ago.[7]

Cyanobacteria

These Algae haveprimarychloroplasts, i.e. the chloroplasts are surrounded by two membranes and

probably developed through a single endosymbiotic event. The chloroplasts of Red Algae have

chlorophyllsa and c (often), and phycobilins, while those of Green Algae have chloroplasts withchlorophyll a and b. Higher plants are pigmented similarly to Green Algae and probably developed from

them, and thus Chlorophyta is a sister taxon to the plants; sometimes they are grouped as Viridiplantae.

Green Algae

These groups have green chloroplasts containing chlorophylls a and b. Their chloroplasts aresurrounded byfour and three membranes, respectively, and were probably retained fromingested Green Algae.

Chlorarachniophytes, which belong to the phylum Cercozoa, contain a small nucleomorph,

which is a relict of the algae's nucleus.

Euglenids, which belong to the phylum Euglenozoa, live primarily in freshwater and havechloroplasts with only three membranes. It has been suggested that the endosymbiotic Green

Algae were acquired through myzocytosis rather thanphagocytosis

Red Algae

These groups have chloroplasts containing chlorophyllsa and d, and phycobilins. The latter chlorophyll

type is not known from any prokaryotes or primary chloroplasts, but genetic similarities with the Red

Algae suggest a relationship there.

In the first three of these groups (Chromista), the chloroplast has four membranes, retaining

a nucleomorph in Cryptomonads, and they likely share a common pigmented ancestor, although other


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evidence casts doubt on whether theHeterokonts, Haptophyta, and Cryptomonadsare in fact more

closely related to each other than to other groups.[2][15]

The typical dinoflagellate chloroplast has three membranes, but there is considerable diversity in

chloroplasts within the group, and it appears there were a number of endosymbiotic

events.[1]

TheApicomplexa, a group of closely related parasites, also haveplastids called apicoplasts.

Apicoplasts are not photosynthetic but appear to have a common origin withDinoflagellatechloroplasts.[1]

Symbiotic algae

Some species of algae form symbiotic relationships with other organisms. In these symbioses,

the algae supply photosynthates (organic substances) to the host organism providing protectionto the algal cells. The host organism derives some or all of its energy requirements from the

algae. Examples are as follows.

[edit] Lichens

Main article: Lichens

Rock lichens in Ireland.

Lichens are defined by the International Association for Lichenology to be "an association of afungus and a photosynthetic symbiont resulting in a stable vegetative body having a specificstructure."[24] The fungi, or mycobionts, are from the Ascomycota with a few from the

Basidiomycota. They are not found alone in nature but when they began to associate is notknown.

[25]One mycobiont associates with the same phycobiont species, rarely two, from the

Green Algae, except that alternatively the mycobiont may associate with the same species of


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Cyanobacteria (hence "photobiont" is the more accurate term). A photobiont may be associatedwith many specific mycobionts or live independently; accordingly, lichens are named and

classified as fungal species.[26]

The association is termed a morphogenesis because the lichen hasa form and capabilities not possessed by the symbiont species alone (they can be experimentally

isolated). It is possible that the photobiont triggers otherwise latent genes in the mycobiont.[27]

[edit] Coral reefs

Main articles: Coral, Coral reef, and Zooxanthella

Floridian coral reef

Coral reefs are accumulated from the calcareousexoskeletons ofmarine invertebrates of theScleractinia order; i.e., the StonyCorals. As animals they metabolizesugarand oxygen to obtain

energy for their cell-building processes, including secretion of the exoskeleton, with waterandcarbon dioxide as byproducts. As the reef is the result of a favorable equilibrium between

construction by the corals and destruction by marine erosion, the rate at which metabolism canproceed determines the growth or deterioration of the reef.

Algae of the Dinoflagellate phylum are often endosymbionts in the cells of marine invertebrates,

where they accelerate host-cell metabolism by generating immediately available sugar andoxygen throughphotosynthesis using incident light and the carbon dioxide produced in the host.

Endosymbiont algae in the Stony Corals are described by the term zooxanthellae, with the hostStonyCorals called on that account hermatypic corals, which although not a taxon are not in

healthy condition without their endosymbionts. Zooxanthellae belong almost entirely to thegenus Symbiodinium.[28] The loss ofSymbiodinium from the host is known as coral bleaching, a

condition which unless corrected leads to the deterioration and loss of the reef.

[edit] Sea sponges

Main article: Sea sponge

Green Algae live close to the surface of some sponges, for example, breadcrumb sponge(Halichondria panicea). The alga is thus protected from predators; the sponge is provided withoxygen and sugars which can account for 50 to 80% of sponge growth in some species.

[29]


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Red Algae

These groups have chloroplasts containing chlorophylls a and d, and phycobilins. The latter

chlorophyll type is not known from any prokaryotes or primary chloroplasts, but geneticsimilarities with the Red Algae suggest a relationship there.

In the first three of these groups (Chromista), the chloroplast has four membranes, retaining a

nucleomorph in Cryptomonads, and they likely share a common pigmented ancestor, althoughother evidence casts doubt on whether the Heterokonts, Haptophyta, and Cryptomonads are in

fact more closely related to each other than to other groups.[2][15]

The typical dinoflagellate chloroplast has three membranes, but there is considerable diversity inchloroplasts within the group, and it appears there were a number of endosymbiotic events.

[1]

The Apicomplexa, a group of closely related parasites, also haveplastids called apicoplasts.

Apicoplasts are not photosynthetic but appear to have a common origin with Dinoflagellatechloroplasts.[


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Fungus

From Wikipedia, the free encyclopedia

Jump to: navigation, search"Fungi" redirects here. You may be looking forFungi (music), Fungus (XM) orFungus the

Bogeyman.

FungiFossil range: Early Devonian Recent (but see

text)Pre

OSDCPTJKPgN


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Clockwise from top left: Amanita muscaria, a

basidiomycete; Sarcoscypha coccinea, an

ascomycete; bread covered in mold; a chytrid; a

Penicilliumconidiophore.Scientific classification

Domain: Eukaryota

(unranked): Opisthokonta

Kingdom: Fungi

(L., 1753) R.T. Moore, 1980[1]

Subkingdoms/Phyla/Subphyla[2]

BlastocladiomycotaChytridiomycota

Glomeromycota

MicrosporidiaNeocallimastigomycota

Dikarya (inc. Deuteromycota)

AscomycotaPezizomycotinaSaccharomycotina

TaphrinomycotinaBasidiomycota

Agaricomycotina

PucciniomycotinaUstilaginomycotina

Subphyla Incertae sedis

EntomophthoromycotinaKickxellomycotina

Mucoromycotina


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Zoopagomycotina

A fungus (pronounced /fs/) is a member of a large group ofeukaryotic organisms that

includes microorganisms such as yeasts and molds, as well as the more familiarmushrooms. The

Fungi (pronounced /fnda/ or /fa/) are classified as a kingdom that is separate from

plants, animals andbacteria. One major difference is that fungal cells have cell walls that containchitin, unlike the cell walls of plants, which contain cellulose. These and other differences show

that the fungi form a single group of related organisms, named the Eumycota (true fungi orEumycetes), that share a common ancestor(a monophyletic group). This fungal group is distinct

from the structurally similarslime molds (myxomycetes) and water molds (oomycetes). Thediscipline ofbiology devoted to the study of fungi is known as mycology, which is often

regarded as a branch ofbotany, even though genetic studies have shown that fungi are moreclosely related to animals than to plants.

Abundant worldwide, most fungi are inconspicuous because of the small size of their structures,and theircryptic lifestyles in soil, on dead matter, and as symbionts of plants, animals, or other

fungi. They may become noticeable when fruiting, either as mushrooms or molds. Fungi performan essential role in the decomposition of organic matter and have fundamental roles in nutrient

cycling and exchange. They have long been used as a direct source of food, such as mushroomsand truffles, as a leavening agent for bread, and in fermentation of various food products, such as

wine,beer, and soy sauce. Since the 1940s, fungi have been used for the production ofantibiotics, and, more recently, various enzymes produced by fungi are used industrially and in

detergents. Fungi are also used asbiological agents to control weeds and pests. Many speciesproducebioactive compounds called mycotoxins, such as alkaloids andpolyketides, that are

toxic to animals including humans. The fruiting structures of a few species containpsychotropiccompounds and are consumed recreationally or in traditional spiritual ceremonies. Fungi can

break down manufactured materials and buildings, and become significantpathogens of humans

and other animals. Losses of crops due to fungal diseases (e.g. rice blast disease) or foodspoilage can have a large impact on human food supplies and local economies.

The fungus kingdom encompasses an enormous diversity oftaxa with varied ecologies, life cyclestrategies, and morphologies ranging from single-celled aquatic chytrids to large mushrooms.

However, little is known of the truebiodiversity of Kingdom Fungi, which has been estimated ataround 1.5 million species, with about 5% of these having been formally classified. Ever since

the pioneering 18th and 19th century taxonomical works ofCarl Linnaeus, Christian HendrikPersoon, and Elias Magnus Fries, fungi have been classified according to their morphology (e.g.,

characteristics such as spore color or microscopic features) orphysiology. Advances inmolecular genetics have opened the way forDNA analysis to be incorporated into taxonomy,

which has sometimes challenged the historical groupings based on morphology and other traits.Phylogenetic studies published in the last decade have helped reshape the classification of

Kingdom Fungi, which is divided into one subkingdom, sevenphyla, and ten subphyla.

Characteristics

Before the introduction ofmolecular methods for phylogenetic analysis, taxonomists considered

fungi to be members of the Plant Kingdom because of similarities in lifestyle: both fungi and


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plants are mainly immobile, and have similarities in general morphology and growth habitat.Like plants, fungi often grow in soil, and in the case ofmushrooms form conspicuous fruiting

bodies, which sometimes bear resemblance to plants such as mosses. The fungi are nowconsidered a separate kingdom, distinct from both plants and animals, from which they appear to

have diverged around one billion years ago.[6][7]

Some morphological, biochemical, and genetic

features are shared with other organisms, while others are unique to the fungi, clearly separatingthem from the other kingdoms:

Shared features:

y With other eukaryotes: As other eukaryotes, fungal cells contain membrane-boundnuclei with

chromosomes that contain DNA with noncoding regions called introns and coding regions called

exons. In addition, fungi possess membrane-bound cytoplasmic organelles such as

mitochondria, sterol-containing membranes, and ribosomes of the 80S type.[8]

They have a

characteristic range of soluble carbohydrates and storage compounds, including sugar alcohols

(e.g., mannitol), disaccharides, (e.g., trehalose), and polysaccharides (e.g., glycogen, which is

also found in animals[9]

).

y With animals: Fungi lack chloroplasts and are heterotrophic organisms, requiring preformed

organic compounds as energy sources.[10]

y With plants: Fungi possess a cell wall[11]

and vacuoles.[12]

They reproduce by both sexual and

asexual means, and like basal plant groups (such as ferns and mosses) produce spores. Similar to

mosses and algae, fungi typically have haploid nuclei.[13]

y With euglenoids and bacteria: Higher fungi, euglenoids, and some bacteria produce the amino

acidL-lysine in specific biosynthesis steps, called the -aminoadipate pathway.[14][15]

y The cells of most fungi grow as tubular, elongated, and thread-like (filamentous) structures and

are called hyphae, which may contain multiple nuclei and extend at their tips. Each tip contains

a set of aggregated vesiclescellular structures consisting ofproteins, lipids, and other organic

moleculescalled Spitzenkrper.[16]

Both fungi and oomycetes grow as filamentous hyphal

cells.[17] In contrast, similar-looking organisms, such as fi lamentous green algae, grow byrepeated cell division within a chain of cells.

[9]

y In common with some plant and animal species, more than 60 fungal species display the

phenomenon ofbioluminescence.[18]

Unique features:

y Some species grow as single-celled yeasts that reproduce by budding or binary fission.

Dimorphic fungi can switch between a yeast phase and a hyphal phase in response to

environmental conditions.[19]

y The fungal cell wall is composed ofglucans and chitin; while the former compounds are also

found in plants and the latter in the exoskeleton ofarthropods,

[20][21]

fungi are the onlyorganisms that combine these two structural molecules in their cell wall. In contrast to plants

and the oomycetes, fungal cell walls do not contain cellulose.[22]


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Omphalotus nidiformis, a bioluminescent mushroom

Most fungi lack an efficient system for long-distance transport of water and nutrients, such as the

xylem andphloem in many plants. To overcome these limitations, some fungi, such asArmillaria, form rhizomorphs,[23] that resemble and perform functions similar to the roots of

plants. Another characteristic shared with plants includes abiosynthetic pathway for producingterpenes that uses mevalonic acid andpyrophosphate as chemical building blocks.

[24]However,

plants have an additional terpene pathway in their chloroplasts, a structure fungi do notpossess.

[25]Fungi produce several secondary metabolites that are similar or identical in structure

to those made by plants.[24]

Many of the plant and fungal enzymes that make these compoundsdiffer from each other in sequence and other characteristics, which indicates separate origins and

evolution of these enzymes in the fungi and plants.[24][26]

Morphology

[edit] Microscopic structures

An environmental isolate ofPenicillium

1. hypha 2. conidiophore 3. phialide 4. conidia 5. septa


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Most fungi grow as hyphae, which are cylindrical, thread-like structures 210 m in diameterand up to several centimeters in length. Hyphae grow at their tips (apices); new hyphae are

typically formed by emergence of new tips along existing hyphae by a process called branching,or occasionally growing hyphal tips bifurcate (fork) giving rise to two parallel-growing

hyphae.[38]

The combination of apical growth and branching/forking leads to the development of

a mycelium, an interconnected network of hyphae.

[19]

Hyphae can be either septate orcoenocytic: septate hyphae are divided into compartments separated by cross walls (internal cellwalls, called septa, that are formed at right angles to the cell wall giving the hypha its shape),

with each compartment containing one or more nuclei; coenocytic hyphae are notcompartmentalized.

[39]Septa havepores that allow cytoplasm, organelles, and sometimes nuclei

to pass through; an example is the dolipore septum in the fungi of the phylum Basidiomycota.[40]

Coenocytic hyphae are essentially multinucleate supercells.

[41]

Many species have developed specialized hyphal structures for nutrient uptake from living hosts;

examples include haustoria in plant-parasitic species of most fungal phyla, and arbuscules ofseveral mycorrhizal fungi, which penetrate into the host cells to consume nutrients.

[42]

Although fungi are opisthokontsa grouping of evolutionarily related organisms broadly

characterized by a single posteriorflagellumall phyla except for the chytrids have lost theirposterior flagella.

[43]Fungi are unusual among the eukaryotes in having a cell wall that, in

addition to glucans (e.g., -1,3-glucan) and other typical components, also contains thebiopolymerchitin.

[44]

[edit] Macroscopic structures

Armillaria ostoyae

Fungal mycelia can become visible to the naked eye, for example, on various surfaces andsubstrates, such as damp walls and on spoilt food, where they are commonly called mold.Mycelia grown on solid agarmedia in laboratorypetri dishes are usually referred to as colonies.

These colonies can exhibit growth shapes and colors (due to spores orpigmentation) that can beused as diagnostic features in the identification of species or groups.

[45]Some individual fungal

colonies can reach extraordinary dimensions and ages as in the case of a clonal colony of


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Armillaria ostoyae, which extends over an area of more than 900 ha, with an estimated age ofnearly 9,000 years.

[46]

The apotheciuma specialized structure important in sexual reproduction in the ascomycetes

is a cup-shaped fruiting body that holds the hymenium, a layer of tissue containing the spore-

bearing cells.

[47]

The fruiting bodies of the basidiomycetes and some ascomycetes can sometimesgrow very large, and many are well-known as mushrooms.

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