BACTERIAL GROWTH AND NUTRITION.pptx

BACTERIAL GROWTH AND NUTRITION

1. BACTERIAL GROWTH AND NUTRITION DR.VAISHALI POSTGRADUATE DEPARTMENT OF MICROBIOLOGY

2. BACTERIAL GROWTH Microbial growth is defined as the increase in the number of cells, which occurs by cell division. • Binary fission (equal cell division): A cell duplicates its components and divides into two cells. Septum: A partition that grows between two daughter cells and they separate at this location. Generation time: 20 mins appox . • Budding (unequal cell division): A small, new cell develops from surface of exisiting cell and subsequently separates from parent cell

3. BACTERIAL GROWTH CURVE Consider a bacterium introduced into a fresh, nutrient medium and incubated. Such organisms display four major phases of growth in batch culture: 1. The lag phase 2. The logarithmic phase 3. The stationary phase 4. The phase of decline

4. The Lag Phase • Organisms do not increase significantly in number • They are metabolically active • Grow in size. Max cell size is obtained. It synthesize enzymes and metabolic intermediates. • Produce large quantities of energy in the form of ATP It varies with different species.

5. The Log Phase • Organisms have adapted to a growth medium • Growth occurs at an exponential (log) rate The cells start dividing and their numbers increase All cells stain uniformly

6. Stationary Phase Cell division stops due to depletion of nutrients and accumulation of toxic metabolites. Gram variabilty seen. 3) The number of live cells stays constant. Decline (Death) Phase 1) Condition in the medium become less and less supportive of cell division 2) Cell lose their ability to divide and leads to cell death 3) Number of live cells decreases at a logarithmic rate

7. BACTERIAL NUTRITION PHYSICAL REQUIREMENTS – Temperature – pH – Oxygen – Hydrostatic Pressure – Osmotic pressure

8. CHEMICAL REQUIREMENTS (NUTRITIONAL FACTORS) – Carbon – Nitrogen, sulfur , and phosphorous – Trace elements – Oxygen – Organic growth factor

9. Optimum pH: the pH at which the microorganism grows best (e.g. pH 7) . Most bacteria grow between pH 6.5 and 7.5 Molds and yeasts grow between pH 5 and 6 According to their tolerance for acidity/alkalinity, bacteria are classified as: Acidophiles (acid-loving): grow best at pH 0.1-5.4 Neutrophiles : grow best at pH 5.4 to 8.0 Alkaliphiles (base-loving): grow best at pH 7.0-11.5

10. Temperature According to their growth temperature range, bacteria can be classified as: Psychrophiles : grow best at 15-20 C Psychrotrophs : grow between 0°C and 20–30°C Mesophiles : grow best at 25-40 C Thermophiles : grow best at 50-60 C Typical Growth Rates and Temperature Minimum growth temperature: lowest temp which species can Grow. Optimum growth temperature: temp at which the species grow Best. Maximum growth temperature: highest temp at which grow is Possible.

11. Oxygen • Aerobes: require oxygen to grow • Obligate aerobes : must have free oxygen for aerobic respiration (e.g. Pseudomonas ) • Anaerobes : do not require oxygen to grow • Obligate anaerobes: killed by free oxygen (e.g. Bacteroides ) • Microaerophiles : grow best in presence of small amount of free oxygen

12. CONT.. • Capnophiles : carbon-dioxide loving organisms that thrive under conditions of low oxygen • Facultative anaerobes : carry on aerobic metabolism when oxygen is present, but shift to anaerobic metabolism when oxygen is absent • Aero tolerant anaerobes: can survive in the presence of oxygen but do not use it in their metabolism • Obligate: organism must have specified environmental condition • Facultative: organism is able to adjust to and tolerate environmental condition, but can also live in other conditions

13. Hydrostatic Pressure • Water in oceans and lakes exerts pressure exerted by standing water, in proportion to its depth. • Barophiles : bacteria that live at high pressures, but die if left in laboratory at standard atmospheric pressure. Halophiles Salt-loving organisms which require moderate to large quantities of salt (sodium chloride)

14. Osmotic Pressure • Environments that contain dissolved substances exert osmotic pressure, and pressure can exceed that exerted by dissolved substances in cells. • Hyperosmotic environments: cells lose water and undergo plasmolysis (shrinking of cell ). • Hypoosmotic environment: cells gain water and swell and burst.

15. Chemical Requirement: Nutritional Factors 1. Carbon sources 2. Nitrogen sources 3. Sulfur and phosphorus 4. Trace elements (e.g. copper, iron, zinc, and cobalt) 5. Vitamins (e.g. folic acid, vitamin B-12, vitamin K)

16. Carbon – Structural organic molecules, energy source – Chemoheterotrophs use organic carbon sources – Autotrophs use CO2Chemical Requirements Nitrogen – In amino acids and proteins – Most bacteria decompose proteins – Some bacteria use NH4+ or NO3– – A few bacteria use N2 in nitrogen fixation

17. • Sulfur – In amino acids, thiamine, and biotin – Most bacteria decompose proteins – Some bacteria use SO4 2– or H2S • Phosphorus – In DNA, RNA, ATP, and membranes – PO4 3– is a source of phosphorusChemical Requirements

18. • Trace elements – Inorganic elements (mineral) required in small amounts – Usually as enzyme cofactors – Ex: iron, molybdenum, zinc • Buffer – To neutralize acids and maintain proper pH – Peptones and amino acids or phosphate salts may act as buffers

19. Organic Growth Factors • Organic compounds obtained directly from the environment • Ex: Vitamins, amino acids, purines, and pyrimidines

20. MECHANICAL AND SONIC STRESS: - Bacterial cell walls may be ruptured by mechanical stress such as vigorous shaking. - It is also disintegrated by exposure to ultrasonic vibration.

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