Lecture 3. Microbial Physiology

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1 Micro-Biology For 3 rd Sem. Students of ISM-IUK, Bishkek Lecture 3 Microbial Physiology

2 LECTURE OBJECTIVES 1. Bacterial Growth 2. Growth Requirements 3. Nutritional types of microorganisms 4. Enzymes, Metabolism, and Energy 5. Cultivation of microorganisms

3 Physiology of bacteria (definition, goal) the science is studying: activity, metabolism of bacteria, nutrition, production of energy and their reproduction, interaction with environment. for identification for studying pathogenesis infection diseases, diagnosis, treatment and prevention, regulation of relationship between human and environment, using biotechnology for synthesis bioactive substances.

4 Composition of bacterial cell Water - 80% (spores %) Proteins % (dry solid mater), more than 2000 proteins, functions: metabolism, structure, enzyme activity,antigenicity,immunogenicity, virulence Nucleic acid: DNA, RNA Carbohydrates: mono- and polysacharides, functions: structure (capsule), nutrients Lipids - no more 40%, functions: membrane structures, nutrients Mineral substances

5 I. Growth Cycle Bacteria divide by binary fission. Growth cycle has 4 phases. 1. Lag phase initial period when vigorous metabolic activity occurs but cells do not divide. 2. Log or Exponential phase - Cells number increase in a logarithmic manner. 3. Stationary phase cell division stops due to depletion of nutrients and accumulation of toxic products. 4. Death phase this is phase when the population decreases due to cell death.

6 The bacterial growth curve:

7 II. 1. Nutrition: Carbon Nitrogen Inorganic ions: a) Phosphate b) Sulfate c) Iron d) Mg e) K f) N* g) Ca++ GROWTH REQUIREMENTS Essential metabolites: Many bacteria have lost the ability to synthesize one or more essential nutrients & so require it; Amino acids Vitamins Hemin NAD

8 2. Environment conditions Temperature: mesophiles - microbes that thrive at 20 to 40 o C; psychrophiles are capable growth at freezing point tempetatures (0-20 o C); thermophiles - above 45 oc H-ion Concentration(pH): acidophilic (ph 2 to 5); neutrophils (6-8); alkaliphiles (above 8,5)

9 Types of microorganisms by oxygen requirements: Obligate aerobes - require oxygen to grow because their ATP-generating system is dependent on oxygen as the hydrogen acceptor Nocardia Bacillus cereus Mycobacteria Meningococci Pseudomonas Bordetella Legionella Brucella

10 Types of microorganisms by oxygen requirements: Facultative anaerobes (facultatives) - utilize oxygen to generate energy by respiration if it is present, but they can use the fermentation pathway to synthesize ATP in the absence of sufficient oxygen. Staphylococcus Bacillus anthracis Listeria Corynebacterium Actinomyces Mycoplasma E. coli Shigella Salmonella

11 Types of microorganisms by oxygen requirements: Obligate anaerobes that does not require oxygen for survival; can exist in the absence of oxygen Clostridium Bacteroids Microaerophilics grow in the presence of O2, but can not use it as a final H+ acceptors and derive their energy solely from fermentative reactions.(lactic acid bacteria and streptococci) Streptococcus Spirochetes Campylobacter

12 Influence of environmental factors 1. Temperature: 2. Moisture: drying, dehydration/lyophilization 3. Osmotic pressure: hypertonic, hypotonic solitons - lysis 4. H-ion Concentration(pH) 5. Gases: oxygen, CO2 6. Light: ultraviolet 7. Chemicals: disinfectants, antibiotics

13 III. Nutritional types of microorganisms Phototroph - organisms able to convert light energy into chemical energy and the process by which they do that is called photosynthesis. Chemotrophs - use either inorganic or organic chemicals as an energy source Autotroph - use carbon dioxide (CO2) as their carbon source (plants, algae, cyanobacteria) Lithotrophs - use other inorganic compounds (plants) Heterotrophs - use organic compounds (all animals, inc. humans, protozoa, fungi)

14 Nutritional types in bacterial metabolism Nutritional type Source of energy Source of carbon Examples Phototrophs Sunlight Organic compounds (photoheterotrophs) or carbon fixation (photoautotrophs) Cyanobacteria, Green sulfur bacteria, Chloroflexi, or Purple bacteria Lithotrophs Inorganic compounds Organic compounds (lithoheterotrophs) or carbon fixation (lithoautotrophs) Thermodesulfobacteria, Hydrogenophilaceae, or Nitrospirae Organotrophs Organic compounds Organic compounds (chemoheterotrophs) or carbon fixation (chemoautotrophs) Bacillus, Clostridium or Enterobacteriaceae

15 Bacterial metabolism Metabolic reactions are enhanced and regulated by enzymes. Enzyme a protein molecule that catalyzes biochemical reactions. 6 classes: 1. Oxyreductase 2. Transferase 3. Hydrolase 4. Ligase 5. Lyase 6. Isomerase

16 Pathogenic enzymes Colagenase Hyaluronidase Coagulase Ig A Protease Leukocidins Streptokinase

17 Bacterial metabolism Metabolism the sum of all chemical reactions occurring in a cell; consist of anabolism and catabolism. Metabolic reactions are enhanced and regulated by enzymes. Anabolism the part of metabolism concerned with building of large compounds from smaller compounds; involves the creation of chemical bonds; requires energy; such chemical reactions (anabolic or biosynthetic reactions) Catabolism - the part of metabolism concerned with breaking down large compounds into smaller compounds; involves the breaking of chemical bonds; energy is released (catabolic or degradative reactions)

18 Heterotrophic metabolism is the biologic oxidation of organic compounds, such as glucose, to yield ATP and simpler organic (or inorganic) compounds, which are needed by the bacterial cell for biosynthetic or assimilatory reactions. Respiration is a type of heterotrophic metabolism that uses oxygen and in which 38 moles of ATP are derived from the oxidation of 1 mole of glucose, yielding 380,000 cal. (An additional 308,000 cal is lost as heat.) Fermentation - another type of heterotrophic metabolism, an organic compound rather than oxygen is the terminal electron (or hydrogen) acceptor. Less energy is generated from this incomplete form of glucose oxidation, but the process supports anaerobic growth.

19 Krebs Cycle The Krebs cycle is the oxidative process in respiration by which pyruvate (via acetyl coenzyme A) is completely decarboxylated to C0 2. The pathway yields 15 moles of ATP (150,000 calories). Glyoxylate Cycle The glyoxylate cycle, which occurs in some bacteria, is a modification of the Krebs cycle. Acetyl coenzyme A is generated directly from oxidation of fatty acids or other lipid compounds. Electron Transport and Oxidative Phosphorylation In the final stage of respiration, ATP is formed through a series of electron transfer reactions within the cytoplasmic membrane that drive the oxidative phosphorylation of ADP to ATP. Bacteria use various flavins, cytochrome, and nonheme iron components as well as multiple cytochrome oxidases for this process.

20 AEROBIC GROWTH The organisms an adequate supply of oxygen enhances metabolism and growth. The oxygen acts as the hydrogen acceptor in the final steps of energy production catalyzed by the flavoproteins and cytochromes. The microorganism use of oxygen generates 2 toxic molecules, hydrogen peroxide and the free radical superoxide bacteria require 2 enzymes to utilize oxygen.

21 Anaerobic growth An anaerobic biochemical pathway in which substance are broken down and energy and reduced compounds are produced; oxygen does not participate in the process This process is known as fermentation and leads to the formation of several organic products (acids, alcohols, gas)

22 I. In vitro: 1. Cultivation on nutrient media - bacteria Simple agar, blood agar, chocolate agar, MacConkey 2. Cultivation in tissue culture - chlamydia, rickettsiae in cell culture - viruses human cell lines animals cell lines II. In vivo: V. Cultivation of microorganisms 1. Chicken s embryo - chlamydia, rickettsiae, viruses 2. Laboratory animals (mouse, rat, rabbit, monkey, pig) - bacteria, chlamydia, rickettsiae, viruses III. PCR - multiplication of genome, proteins

23 Culture Media 1. Classification by consistency: Liquid media or broths e.g nutrient broth Solid media Semi-solid agar Biphasic media 2. Classification by nutritional component: Simple Complex Synthetic Defined, semi-defined.

25 3. Classification by functional use or application: Basal media Enriched media Selective media Differential media or indicator media Transport media Anaerobic media Media for Biochemical reaction For more joins us facebook

Bacterial Growth, Nutritional Requirements and Physical Growth Factors

Bacterial Growth, Nutritional Requirements and Physical Growth Factors Bacterial Growth Growth of Bacteria Bacterial growth involves both an increase in the size of organisms and an increase in their number.