Bacterial physiology

Eri dian

Microbial Physiology

Nutritional factors for microbial growth

Environmental factors for microbial growth

Microbial metabolism

Nutritional factors for microbial growth

• Bacteria, like all living organisms, require

nutrients for metabolic purposes and for

cell division, and grow.

• Chemically, bacteria are made up of : polysaccharide, protein, lipid, nucleic acid and

peptidoglycan

# Carbon source

- Autotrophs (lithotrophs): use CO2 as the C source

Photosynthetic autotrophs: use light energy

Chemolithotrophs: use inorganics

- Heterotrophs (organotrophs): use organic carbon (eg.

glucose) for growth.

# Nitrogen source

Ammonium (NH4+) is used as the sole N source by most

microorganisms. Ammonium could be produced from N2 by

nitrogen fixation, or from reduction of nitrate (NO3-)and nitrite

(NO2).

Metabolic Requirements

# Sulfur source

A component of several coenzymes and amino acids.

Most microorganisms can use sulfate (SO42-) as the S source.

# Phosphorus source

- A component of ATP, nucleic acids, coenzymes,

phospholipids, teichoic acid, capsular polysaccharides; also is

required for signal transduction.

- Phosphate (PO43-) is usually used as the P source.

Metabolic Requirements

# Mineral source

- Required for enzyme function.

- For most microorganisms, it is necessary to provide sources

of K+, Mg2+, Ca2+, Fe2+, Na+ and Cl-.

- Many other minerals (eg., Mn2+, Mo2+, Co2+, Cu2+ and Zn2+)

can be provided in tap water or as contaminants of other

medium ingredients.

- Uptake of Fe is facilitated by production of siderophores

(Iron-chelating compound, eg. Enterobactin).

# Growth factors: organic compounds (e.g., amino acids, sugars,

nucleotides) a cell must contain in order to grow but which it is unable

to synthesize.

Organic coumpound

• Organic nutrients are essential in different amounts, depending

on the bacterial species.

• Carbohydrates are used as an energy source and as an initial substrate for biosynthesis of many substances.

• Amino acids are crucial for growth of some bacteria.

• Vitamins, purines and pyrimidines in trace amounts are needed for growth and as catalisator.

Essential Elements

Environmental factors for microbial growth • Temperature

Psychrophile (15 oC - 20 oC)

Mesophile (30 oC - 37 oC)

Thermophile (50 oC - 60 oC)

• pH

Neutrophile (pH 6 - 8)

Acidophile (pH 1-5)

Alkaliphile (pH 9-11)

• Oxygen availability

Obligate aerobe

Obligate anaerobe

Facultative anaerobe

Microaerophile (5-10% O2

(Capnophilics: bacteria that do not produce enough CO2 and, therefore, require additional CO2 for growth.)

• Water availability

Osmophile: microorganisms

adapted to environments with

high osmotic pressures, such as

high sugar concentrations

Osmophiles are similar to halophillic (salt-loving) organisms because a critical aspect of both types of environment is their low water activity. Nearly all osmophilic microorganisms are from the yeast genus.

Oxygen and Hiydrogen for microbial growth

• Oxygen & hydrogen are obtained from water;

• Water is essential for bacterial growth

• correct oxygen tension is necessary for balanced growth

Obligate aerobe

Facultative anaerobe

Obligate anaerobe

Microaerophile

1. O2 reduced to H2O2 by enzymes.

2. O2 reduced to O2- by ferrous ion.

3. In aerobes and aerotolerant anaerobes, O2

- is removed by “superoxide dismutase”, while H2O2 is removed by “catalase”.

4. Strict anaerobes lack both catalase and superoxide

dismutase.

Toxicity of O2 for Anaerobes

Excluding oxygen

Reducing agents, Na-

tioglikolat

Anaerobic jar

Anaerobic glove chamber

Anaerobic cultivation methods

Redox Reactions

• All chemical reactions consist of transferring electrons from a donor to an acceptor

• Chemicals that donate electrons become oxidized.

• Chemicals that accept electrons become reduced.

Redox Reactions

• Energy is released during these electron transfers.

• In order to capture that energy, bacteria need to intercept the electrons during redox reactions

• Eh is important for clinical in infection wound whether aerob and anaerob population at the same site

Metabolism

• The goal of metabolism is to conserve the energy released during redox reactions by making high energy compounds such as ATP.

• There are different strategies for conserving this energy

Metabolism

• Metabolism to yield energy : 1. respiration 2. fermentation 3. photosynthetic Fermentation

– Transfer of electrons to organic substrate

• Respiration

– Transfer of electrons to inorganic acceptor

– Phoptosynthesis : energy from light is altered to chemical energy in the form of ATP

PETA KONSEP

Proses Metabolisme:

Anabolisme

Katabolisme

Karbohidrat, Lemak, Protein

Proses sintesis sel dan enzim, memelihara steady state sel, penyerapan unsur hara, ekskresi senyawa, pergerakan sel

Reaksi enzimatik, Reaksi Reduksi- Oksidasi

Energi

– Definisi Metabolisme, Katabolisme dan Anabolisme

– Metabolisme sebagai proses produksi energi untuk kehidupan sel

– Senyawa pembawa energi, ATP dan ADP

DEFINISI METABOLISME

Semua proses kimiawi yang dilakukan oleh organisme atau semua reaksi yang melibatkan transformasi energi kimia di dalam mahluk hidup

Anabolisme: Pembentukan senyawa yang memerlukan energi (Reaksi endergonik):

FOTOSINTESIS: MEMBENTUK C6G12O5 DARI CO2 DAN H2O

Katabolisme: Penguraian senyawa yang menghasilkan energi (Reaksi eksergonik):

RESPIRASI MENGURAIKAN KARBOHIDRAT MENJADI ASAM PIRUVAT DAN ENERGI

Chapter 5

MENGAPA MIKROBA MEMERLUKAN ENERGI ?

• Synthesa bagian sel (dinding sel,

membran sel, dan substansi sel

lainnya)

• Synthesis Enzim, Asam Nukleat,

Polysakarida, Phospholipids, atau

komponen sel lainnya

• Mempertahankan kondisi sel

(optimal) dan memperbaiki bagian

sel yang rusak

• Pertumbuhan dan Perbanyakan

• Penyerapan hara dan ekskresi

senyawa yang tidak diperlukan

atau waste products

• Pergerakan (Motilitas)

ENERGI KIMIA

Komponen kimia berenergi tinggi:

Adenosin Diphosphate (ADP) dan Adenosine Triphosphate (ATP)

yang dibentuk dari Adenosine Monophosphate

ADP adalah AMP ~ P dan ATP adalah AMP ~ P~ P

REAKSI BIOKIMIA DIKATALIS OLEH ENZIM:

Berperan penting dalam setiap reaksi metabolisme

Bacteria Growth • Bacteria reproduce by a process called binary fission

• in which a parent cell divides

• to form a progeny of two cells

• This results in a logarithmic growth rate

• One bacterium will produce 16 bacteria after four generations.

• The doubling or mean generation time of bacteria may vary (e.g. 20 minutes for E. coli, 24 hours for M. tbc)

• The shorter the doubling time, the faster the multiplication rate

• Other factors that affect the doubling time include the amount of

nutrients, the temperature and the pH of the environment

Principles of bacterial growth

Bacteria multiply by binary

fission.

Microbial growth is defined as

an increase in the number of

cells in a population.

Bacterial growth curve

Bacterial growth

Doubling (generation) time

E. coli: 20 min

M. tuberculosis: 12-24 h

The growth cycle of a bacterium • Four main phases 1. Lag phase: may last for a few minutes or for many hours as bacteria do not

divide immediately but undergo a period of adaptation with vigorous metabolic activity.

2. Log (logarithmic, exponential) phase: rapid cell division occurs, determined by the environmental conditions.

3. Stationary phase: is reached when nutrient depletion or toxic products cause growth to slow until the number of new cells produced balances the number of cells that die. The bacteria have now achieved their maximal cell density or yield.

• 4. Decline or death phase: this is marked by a decline in the number of live bacteria.

A balance between slow loss of cells through death and the formation of new cells through growth and division.

Bacteria synthesize macromolecules required for multiplication.

The length of lag phase depends on the conditions in the original culture and the medium into which they are transferred.

The doubling time is measured during this period.

The bacteria are most susceptible to antibiotics during this time. Bacteria stop growing due to decrease of nutrients and O2 supply, and accumulation of toxic metabolites.