Chair of Medical Biology, Microbiology, Virology, and Immunology

THE PHYSIOLOGY OF THE PHYSIOLOGY OF MICROORGANISMS.MICROORGANISMS.

Lecturer As. Prof. O. Pokryshko

Lecture scheduleLecture schedule

1.1. Growth of bacteria.Growth of bacteria.2.2. Reproduction of bacteria.Reproduction of bacteria.3.3. Respiration of bacteria.Respiration of bacteria.

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Carbon sourcesCarbon sources HeterotrophHeterotroph – must obtain carbon in an – must obtain carbon in an

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

AutotrophAutotroph - an organism that uses CO - an organism that uses CO22, an , an

inorganic gas as its carbon sourceinorganic gas as its carbon source not nutritionally dependent on other living thingsnot nutritionally dependent on other living things

Nutritional TypesNutritional Types

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Nitrogen SourcesNitrogen Sources

Main reservoir is nitrogen gas (NMain reservoir is nitrogen gas (N22); );

79% of earth’s atmosphere is N79% of earth’s atmosphere is N2.2.

Nitrogen is part of the structure of Nitrogen is part of the structure of proteins, DNA, RNA & ATP – these proteins, DNA, RNA & ATP – these are the primary source of N for are the primary source of N for heterotrophs.heterotrophs.

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Nitrogen SourcesNitrogen Sources

Some bacteria & algae use inorganic N Some bacteria & algae use inorganic N nutrients (NOnutrients (NO33

--, NO, NO22--, or NH, or NH33).).

Some bacteria can fix NSome bacteria can fix N2.2.

Regardless of how N enters the cell, it Regardless of how N enters the cell, it must be converted to NHmust be converted to NH33, the only , the only

form that can be combined with carbon form that can be combined with carbon to synthesis amino acids, etc.to synthesis amino acids, etc.

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Energy sourceEnergy sourcechemotrophchemotroph – gain energy from – gain energy from chemical compoundschemical compoundsphototrophsphototrophs – gain energy through – gain energy through photosynthesisphotosynthesis

Nutritional TypesNutritional Types

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Transport: Movement of Transport: Movement of Chemicals Across the Cell Chemicals Across the Cell

MembraneMembrane Passive transportPassive transport –does not require energy; –does not require energy;

substances exist in a gradient and move from substances exist in a gradient and move from areas of higher concentration towards areas of areas of higher concentration towards areas of lower concentrationlower concentration diffusiondiffusion osmosis – diffusion of waterosmosis – diffusion of water facilitated diffusion – requires a carrierfacilitated diffusion – requires a carrier

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Transport: Movement of Transport: Movement of Chemicals Across the Cell Chemicals Across the Cell

MembraneMembrane Active transportActive transport – requires energy and carrier – requires energy and carrier

proteins; gradient independentproteins; gradient independent active transportactive transport group translocation – transported molecule group translocation – transported molecule

chemically alteredchemically altered

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Gas RequirementsGas RequirementsOxygenOxygen As oxygen is utilized it is transformed into As oxygen is utilized it is transformed into

several toxic products:several toxic products: singlet oxygen (Osinglet oxygen (O22), superoxide ion (O), superoxide ion (O22

--), ), peroxide (Hperoxide (H22OO22), and hydroxyl radicals (OH), and hydroxyl radicals (OH--))

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

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

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Categories of Oxygen Categories of Oxygen RequirementRequirement

AerobeAerobe – utilizes oxygen and can – utilizes oxygen and can detoxify itdetoxify it

obligate aerobeobligate aerobe - cannot grow - cannot grow without oxygen without oxygen

facultative anaerobefacultative anaerobe – utilizes – utilizes oxygen but can also grow in its oxygen but can also grow in its absenceabsence

microaerophylicmicroaerophylic – requires only a – requires only a small amount of oxygensmall amount of oxygen

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Categories of Oxygen Categories of Oxygen RequirementRequirement

AnaerobeAnaerobe – does not utilize oxygen – does not utilize oxygen obligate anaerobeobligate anaerobe - lacks the - lacks the

enzymes to detoxify oxygen so cannot enzymes to detoxify oxygen so cannot survive in an oxygen environmentsurvive in an oxygen environment

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

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Carbon Dioxide Carbon Dioxide RequirementRequirement

All microbes require some carbon All microbes require some carbon dioxide in their metabolism.dioxide in their metabolism.

capneiccapneic – grows best at higher CO – grows best at higher CO22 tensions than normally present in the tensions than normally present in the atmosphereatmosphere

Oxygen requirementsOxygen requirements

Aerobic culture Anaerobic culture Microaerobic culture

1. 1. 1.2. 2. 2.

3. 4. 3. 4. 3. 4.

1. 2. 3. 4.

1. Obligate anaerobe2. Facultative anaerobe3. Microaerophile4. Obligate aerobe

Growth requirementsGrowth requirements

TemperatureTemperature Pyschrophiles Pyschrophiles 4-20°C4-20°C MesophilesMesophiles 15-48°C15-48°C ThermophilesThermophiles 42-68°C42-68°C Extreme thermophilesExtreme thermophiles >68°C>68°C

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Effects of pHEffects of pH Majority of microorganisms grow at a Majority of microorganisms grow at a

pH between 6 and 8pH between 6 and 8 Obligate acidophilesObligate acidophiles – grow at – grow at

extreme acid pHextreme acid pH AlkalinophilesAlkalinophiles – grow at extreme – grow at extreme

alkaline pHalkaline pH

The Population Growth CurveThe Population Growth Curve In laboratory studies, populations typically display In laboratory studies, populations typically display a predictablea predictable pattern over time – pattern over time – growth curve.growth curve.

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The Population Growth CurveThe Population Growth Curve

Stages in the normal growth Stages in the normal growth curve:curve:

1.1. ______phase______phase – “flat” period of adjustment, – “flat” period of adjustment, enlargement; little growthenlargement; little growth

2.2. _____________________ phase_____________________ phase – a period – a period of maximum growth will continue as long of maximum growth will continue as long as cells have adequate nutrients and a as cells have adequate nutrients and a favorable environmentfavorable environment

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The Population Growth CurveThe Population Growth Curve

Stages in the normal growth curve:Stages in the normal growth curve:

1.1. _________ phase_________ phase – rate of cell growth equals – rate of cell growth equals rate of cell death caused by depleted nutrients rate of cell death caused by depleted nutrients and Oand O22, excretion of organic acids and , excretion of organic acids and pollutantspollutants

2.2. _________ phase_________ phase – as limiting factors – as limiting factors intensify, cells die exponentially in their own intensify, cells die exponentially in their own wasteswastes

Nutrient mediaNutrient media

Ordinary (simple) mediaOrdinary (simple) media Special mediaSpecial media (serum agar, serum (serum agar, serum

broth, coagulated serum, pota toes, broth, coagulated serum, pota toes, blood agar, blood broth, etc.).blood agar, blood broth, etc.).

Elective mediaElective media Enriched mediaEnriched media

Nutrient mediaNutrient media

Differential diagnostic media:Differential diagnostic media: (1) (1) proteolytic action; proteolytic action;

(2) fermentation of carbohydrates (Hiss (2) fermentation of carbohydrates (Hiss media); media);

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

organisms; organisms; (5) media containing substances (5) media containing substances

assimilated only by certain microbes.assimilated only by certain microbes.

Biochemical propertiesBiochemical properties

ColoniesColonies

ColoniesColonies

ColoniesColonies

Pure Cultures IsolationPure Cultures Isolation

Isolated colonies obtainingIsolated colonies obtaining