Microbiology, Virology, and Immunology Department

Lecturer Taras I. Pyatkovskyy

1. Chemical composition of bacteria2. Cell metabolism3. Types of microbial nutrition4. Respiration of bacteria5. Growth and reproduction of

microbes6. Bacterial transport systems7. Bacterial enzymes8. Nutrient media9. Isolated colonies obtaining

Carbon source Heterotroph – must obtain carbon

in an organic form made by other living organisms such as proteins, carbohydrates, lipids and nucleic acids

Autotroph - an organism that uses CO2, an inorganic gas as its carbon source not nutritionally dependent on other

living things

Protein 55 %

Total RNA 20.5 %

DNA 3.1 %

Phospholipid 9.1 %

  Lipopolysaccharide  3.4 %

Murein 2.5 %

Inorganic ions  1.0 %

Bacterial cell consists of:

Water – 70-90 % Dry weight – 10-30 % Proteins – 55 %, 2,35 million of molecules, 1850 different types of molecules

RNA – 20,5 %, 250000 molecules, 660 different types of molecules

DNA – 3,1 %, 2 molecules

Lipids – 9 %, 22 million of molecules

Lipopolysaccharides –3,4 %, 1,5 million of molecules

Peptidoglycan – 1 molecule

Microbial metabolism1. Catabolism (Dissimilation)

- Pathways that breakdown

organic substrates

(carbohydrates, lipids, &

proteins) to yield metabolic

energy

for growth and maintenance.

2. Anabolism (Assimilation)

- Assimilatory pathways for

the formation of key

intermediates and then to

end products (cellular

components).

4. Intermediary metabolism -

Integrate two processes

Energy source chemotrophs – gain energy from chemical

compounds phototrophs – gain energy through photosynthesis

Oxygen As oxygen is utilized it is transformed into

several toxic products: singlet oxygen (O2), superoxide ion (O2

-), peroxide (H2O2), and hydroxyl radicals (OH-)

Most cells have developed enzymes that neutralize these chemicals: superoxide dismutase, catalase

If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats.

Aerobe – utilizes oxygen and can detoxify it

obligate aerobe - cannot grow without oxygen

facultative anaerobe – utilizes oxygen but can also grow in its absence

microaerophylic – requires only a small amount of oxygen

Anaerobe – does not utilize oxygen obligate anaerobe - lacks the enzymes

to detoxify oxygen so cannot survive in an oxygen environment

aerotolerance anaerobes – do no utilize oxygen but can survive and grow in its presence

All microbes require some carbon dioxide in their metabolism.

Capnophiles – grows best at higher CO2 tensions than normally present in the atmosphere

TemperaturePyschrophiles 4-20 °CMesophiles 15-48 °CThermophiles 42-68 °CExtreme thermophiles >68 °C

Majority of microorganisms grow at a pH between 6 and 8

Obligate acidophiles – grow at extreme acid pH

Alkalinophiles – grow at extreme alkaline pH

Microbial growth – an increase in a population of microbes rather than an increase in size of an individual

Result of microbial growth is discrete colony – an aggregation of cells arising from single parent cell

Reproduction results in growth

division exactly in half most common means

of bacterial reproduction forming two equal

size progeny genetically identical

offspring cells divide in a

geometric progression doubling cell number

In laboratory studies, populations typically display a predictable pattern over time – growth curve.

Stages in the normal growth curve:

1. lag phase – “flat” period of adjustment, enlargement; little growth

2. exponential or log phase – a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment

Stages in the normal growth curve:

1. stationary phase – rate of cell growth equals rate of cell death caused by depleted nutrients and O2, excretion of organic acids and pollutants

2. death phase – as limiting factors intensify, cells die exponentially in their own wastes

Passive transport –does not require energy; substances exist in a gradient and move from areas of higher concentration towards areas of lower concentrationdiffusionosmosis – diffusion of waterfacilitated diffusion – requires a carrier

Osmosis Osmotic pressure

Active transport – requires energy and carrier proteins; gradient independentactive transportgroup translocation – transported molecule

chemically altered

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Enzymes are biological catalysts that increase the rate of a chemical reaction by lowering the energy of activation

The enzyme is not permanently altered in the reaction

Enzyme promotes a reaction by serving as a physical site for specific substrate molecules to position

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Simple enzymes – consist of protein alone

Conjugated enzymes or holoenzymes – contain protein and nonprotein molecules Apoenzyme – protein portion Cofactors – nonprotein portion

Metallic cofactors: iron, copper, magnesium

Coenzymes, organic molecules: vitamins

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Exoenzymes – transported extracellularly, where they break down large food molecules or harmful chemicals Cellulase, amylase, penicillinase

Endoenzymes – retained intracellularly and function there Most enzymes are endoenzymes

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Bacterial enzymes are subdivided into some groups:

1. Hydrolases which catalyse the breakdown of the link between the carbon and nitrogen atoms, between the oxygen and sulphur atoms, binding one molecule of water (esterases, glucosidases, proteases, amilases, nucleases, etc.).

2. Transferases perform catalysis by transferring certain radicals from one molecule to another (transglucosidases, transacylases. transaminases).

3. Oxidative enzymes (oxyreductases) which catalyse the oxidation-reduction processes (oxidases, dehydrogenases, peroxidases, catalases).

4. Isomerases (Rearrangement atoms of a molecule).

5. Lyases (remove chemical groups from molecules without adding water).

6. Lygases (join two molecules together and usually require energy from ATP).

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Constitutive enzymes – always present, always produced in equal amounts or at equal rates, regardless of amount of substrate Enzymes involved in glucose

metabolism Regulated enzymes – not

constantly present; production is turned on (induced) or turned off (repressed) in response to changes in concentration of the substrate

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Culture media may be found in one of three states:

liquid (called broth) semi-solid solid. Media are solidified by the addition

of solidifying agents such as agar. Varying the concentration of agar

will yield varying degrees of solidification.

Ordinary (simple) media Minimal media Special media (serum agar, serum

broth, coagulated serum, potatoes, blood agar, blood broth, etc.).

Elective media Enriched media Transport media

Differential diagnostic media: (1) proteolytic action; (2) fermentation of carbohydrates

(Hiss media); (3) haemolytic activity (blood agar); (4) reductive activity of micro-

organisms; (5) media containing substances

assimilated only by certain microbes.