Physiology of Bacteria.pptx
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Here are the answers to the MCQs: 1. Binary fission 2. 20 minutes 3. 20 hours 4. 20 days 5. Lag phase 1. Log or exponential 2. Stationary 3. Phase of decline 4. Stationary 5. Log or exponential Psychrophilic Mesophilic Campylobacter spp, Helicobacter spp Neisseria spps, Brucella abortus
Physiology of Bacteria.pptx
- 1. By Dr. Rakesh Prasad Sah Assistant Professor Microbial Growth & Metabolism (Physiology of Bacteria)
- 4. Coccus
- 5. Bacillus
- 7. WHAT IS PHYSIOLOGY ? IT’S THE GROWTH, NUTRITION AND METABOLISM
- 9. Growth It is an increase in all the cell components, which ends in multiplication of cell leading to an increase in population. It involves - an increase in the size of the cell & an increase in the number of individual cells. Bacteria divide by binary fission.
- 10. ve DS DNA Separation of Nuclear strands Formation of new complimentary strands-2 identical DS DNA Transverse septum formed Septal mesosomes involved Septum completed. Cell wall material formed Two daughter cells formed. May remain attached or separate BACTERIAL GROWTH & DIVISION Bacteria divide by binary fission
- 11. Generation time Time required for division of bacterium into two cells in optimal conditions. Ordinary bacterium doubles every 20-30 mins, and their number increases by geometric progression. Theoretically a single bacterium form 10²¹ cells in 24 hrs. But in culture medium (batch culture) cell division ceases/decreases due to exhaustion of nutrients and accumulation of toxic products.
- 12. Generation Time Under Optimal Conditions (at 37oC) Organism Generation Time Bacillus cereus 28 min Escherichia coli 20 min Staphylococcus aureus (causes many types of infections) 27-30 min Mycobacterium tuberculosis (agent of Tuberculosis) 20 hrs Mycobacterium lepra 20 days Treponema pallidum (agent of Syphilis) 30 hrs
- 13. Growth form in Laboratory Colony – formed by bacteria growing on solid media. (20-30 cell divisions) Each bacterial colony represents a clone of cells derived from a single parent cell. Turbidity – liquid media -107-109 cells/ml
- 15. Bacterial counts Growth in numbers can be studied by bacterial counts. 2 methods – Total cell count - Viable cell count
- 16. Total Count Total number of cells in the sample – living + dead. Can be obtained by : 1. Direct counting under microscope using counting chambers. 2. Counting in an electronic device – Coulter counter.
- 17. Viable Cell Count Measures the number of living cells. Methods – Surface colony count 1. Dilution method 2. Plating method Number of colonies that develop after incubation gives an estimate of the viable count.
- 19. Bacterial Growth Curve When a bacterium is added to a suitable medium & incubated, its growth follows a definite course. If bacteria counts are made at intervals after inoculation & plotted in relation to time, a growth curve is obtained. Shows 4 phases : Lag, Log or Exponential Stationary & Phase of Decline.
- 20. Sep 07 Dr Ekta, Microbiology, GMCA
- 22. Phases of Growth Curve Lag phase Immidiately after inoculation – no multiplication. Adapt to new environment. Increase in size due to accumulation of enzymes and metabolites. maximum cell size towards the end of lag phase. Reach the stage of multiplication Period between inoculation and beginning of multiplication is known as lag phase. Duration depends on—species, size of inoculation, nature of culture medium, environmental factors.
- 23. Phases of Growth Curve Log OR Exponential phase – Cell division starts and bacteria increases their number exponentially. E.g. E. coli divides every 20 mins 1248163264 ……so on… smaller cells, stain uniformly (Gram stain) Best stage to perform biochemical tests A straight line is obtained on graph paper.
- 24. Phases of Growth Curve Stationary phase – cell division stops due to depletion of nutrients & accumulation of toxic products. equilibrium exists between dying cells and the newly formed cells, so viable count remains stationary irregular staining (Gram variable) sporulation and production of exotoxins , antibiotics & bacteriocins
- 25. Phase of Decline Viable cell count decreases Bacterial division ceases Exhaustion of nutrients Accumulation of toxic products Cell death by autolytic enzymes Total count pararrels viable count upto end of stationary phase. After this, viable count decreases. Total count remains same, later decreases due to autolysis of cells. Phases of Growth Curve
- 26. Factors Influencing Microbial Growth Temperature Atmosphere – O2 & CO2 H-ion concentration (pH) Moisture & drying Osmotic effects Radiation Mechanical & sonic stress. This scanning electron micrograph (SEM) depicts numerous clumps of methicillin-resistant Staphylococcus aureus bacteria, commonly referred to by the acronym, MRSA, by Janice Haney Carr, PHIL #10046
- 27. Temperature Vary in their temperature requirements. Temperature range – growth does not occur above the maximum or below the minimum. Optimum Temperature – growth occurs best, 37ºC for most pathogenic bacteria.
- 28. Effects of Temperature on Growth 95oF 77oF 40oF Most of our plates are incubated at 37oC (98.6oF).
- 29. Temperature Mesophilic – grows best between 25ºC and 40ºC. e.g. most bacterial pathogens Psychrophilic (cold loving) – grows best below 20ºC e.g. Flavobacterium spps Thermophilic – grows best at high temp, 55- 58ºC e.g. Bacillus stereothermophilus
- 31. Atmosphere Depending on the O2 requirement, bacteria are divided into : 1. Strict (Obligate) Aerobes – require O2 for growth e.g. Pseudomonas aeruginosa 2. Strict (Obligate) Anaerobes – grow in the absence of O2 & may even die on exposure to O2 e.g. Clostridium tetani. 3. Microaerophilic – grow best in the presence of low oxygen levels e.g. Campylobacter spp, Helicobacter spp
- 32. Atmosphere 4. Facultative anaerobe – aerobic but can also grow in the absence of O2 e.g. Staphylococcus spps 5. Aerotolerant anaerobe – anaerobic, but tolerates exposure to O2 e.g. Clostridium perfringens 6. Capnophilic organism – requires high CO2 levels eg Neisseria spps, Brucella abortus.
- 34. H-ion Concentration pH range, optimum pH Neutral or slightly alkaline pH (7.2 – 7.6) – majority of pathogenic bacteria grow best. Lactobacilli – acidic pH Vibrio cholerae – alkaline pH
- 35. Moisture & Drying Water – essential ingredient of bacterial protoplasm. Hence drying is lethal to cells. Effect of drying varies : T.pallidum – highly sensitive Staphylococci sp– stand for months Spores – resistant to dessication, may survive for several decades.
- 36. Osmotic effects More tolerant to osmotic variation due to mechanical strength of their cell walls. Plasmolysis – hypertonic sol - shrinkage Plasmoptysis – from hypotonic sol – D.W. – swelling & rupture of the cell. Radiation X rays & gamma rays exposure – lethal Mechanical & Sonic Stress May be ruptured by mechanical stress. (vigrous shaking and by exposure to ultrasonic vibration)
- 37. Bacterial Nutrition Water constitutes 80% of the total weight of bacterial cells. Proteins, polysaccharides, lipids, nucleic acids, mucopeptides & low molecular weight compounds make up the remaining 20%. For growth & multiplication, the minimum nutritional requirements are water source of carbon, source of nitrogen & some inorganic salts.
- 38. Classification of Bacteria Based on Nutritional Requirement Based on derive of energy Phototrophs – Bacteria which derive their energy from sunlight. Chemotrophs – Bacteria which derive energy from chemical reactions. Based on source of Hydrogen 1. Organotrophs : require organic sources of hydrogen 2. Lithotrophs : require inorganic sources of hydrogen like NH3, H2S
- 39. Classification of Bacteria Based on Nutritional Requirement Based on the utilization of carbon compounds, bacteria are classified as : 1. Autotrophs – can synthesize all their organic compounds by utilizing atmospheric CO2 & N2. No medical importance. 2. Heterotrophs – unable to synthesize their own metabolites & depend on preformed organic compounds.
- 40. Growth Factors Some bacteria require certain organic compounds in minute quantities – Growth Factors OR Bacterial Vitamins. It can be : 1. Essential – when growth does not occur in their absence. 2. Accessory – when they enhance growth, without being absolutely necessary for it.
- 41. Growth Factors Identical with mammalian nutrition Vitamin B complex – 1. Thiamine 2. Riboflavine 3. Nicotinic acid 4. Pyridoxine 5. Folic acid & 6. Vit.B 12
- 42. 1. Bacteria divides by………………….. 2. Generation time of E. coli is………………… 3. Generation time of Mycobacterium tuberculosis is………….. 4. Generation time of Mycobacterium leprae is………….. 5. The time period between inoculation and beginning of multiplication is called………………… MCQs
- 43. 1. Growth of bacteria is exponential in ………………………phase. 2. Growth of bacteria is in equilibrium state in……………………phase. 3. Viable count is decreases in …………………..phase. 4. Complete exhaustion of nutrients and accumulation of toxic products occurs in ……………..phase. 5. Best time to perform Gram staining and biochemical tests in …………….phase.
- 44. Cold loving organisms are also called as……………. Most of the bacterial pathogens are Mesophilic/psychrophilic/Thermophilic? Examples of Microaerophilic microorganisms are………&……… Examples of Capnophilic microorganisms are……………&………