Microbial Growth PDF

Microbial Growth PRESENTED BY- SWARUP MUKHERJEE DEPARTMENT OF MICROBIOLOGY J.K.COLLEGE,PURULIA  What is growth Growth is defined as orderly increase in the quantity of all the cellular components, which is followed by cell division, resul...

Microbial Growth PRESENTED BY- SWARUP MUKHERJEE DEPARTMENT OF MICROBIOLOGY J.K.COLLEGE,PURULIA  What is growth Growth is defined as orderly increase in the quantity of all the cellular components, which is followed by cell division, resulting in increase in cell number.  Difference between growth of unicellular and multicellular organisms. Unicellular organisms Multicellular organisms In unicellular organisms Multicellular organisms like growth is defined as the plants, animals, fission of increasing of entire crop of body cells results only in the organisms rather than increase in size of the a change in individual individual plant or animal, organisms. not in increase in the number of individuals.  Growth of Microbes Increase in number of cells, not cell size One cell becomes colony of millions of cells  GROWTH OF MULTICELLULAR ORGANISM A BABY ELEPHANT GROWS INTO AN ADULT ELEPHANT NOT BECAUSE EACH OF ITS CELL IS LARGER,BUT BECAUSE THE ADULT HAS MORE CELLS.  FACTORS REGULATING GROWTH Nutrients: All organisms need carbon ,hydrogen ,oxygen and a source of electrons for their growth. NUTRIENTS MACRO NUTRIENTS MICRO NUTRIENTS C,O,H,O,N,P,K,Ca,Mg and Fe Mn,Zn,Co,Mo,Ni and Cu required required in relatively large amount. in trace amounts often supplied in water or media components Environmental factor 1.TEMPERATURE 2.GASEOUS REQUIREMENTS 3.HYDROGEN ION CONCENTRATION (pH) 4.MISCELLANEOUS PHYSICAL REQUIREMENTS (Osmotic Pressure , radiation, atmospheric pressure)  GENERATION TIME OF BACTERIA The time taken by the bacteria to double in number during a specified time period is known as the generation time. The generation time tends to vary with different organisms..  Nutritional Categories Carbon sources – CO2 = autotroph – organic = heterotroph Energy sources – sunlight = phototroph – organic = chemotroph  A “Chemoheterotroph” would….. Derive both carbon and energy from organic compounds  A “Chemoorganic autotroph would be…. Derives energy from organic compounds and carbon source from inorganic compounds A related ancient group….. Lithoautotroph Neither sunlight nor organics used, rather it relies totally on inorganics  Nutritional Categories Saprobe – lives on organic matter of dead organisms Parasite – lives on organic matter of living host = pathogens  Temperature Optima Psychrophiles: cold-loving Mesophiles: moderate temperature- loving Thermophiles: heat-loving Each has a minimum, optimum, and maximum growth temperature Fig. 7.8  Temperature Optima Optimum growth temperature is usually near the top of the growth range Death above the maximum temp. comes from enzyme inactivation Mesophiles most common group of organisms 40ºF (5°C) slows or stops growth of most microbes  Oxygen Requirements Obligate aerobes – require O2 Facultative anaerobes – can use O2 but also grow without it Obligate anaerobes – die in the presence of O2  pH Most bacteria grow between pH 6.5 and 7.5 Acid (below pH 4) good preservative for pickles, sauerkraut, cheeses Acidophiles can live at low pH  pH Many bacteria and viruses survive low pH of stomach to infect intestines Helicobacter pylori lives in stomach under mucus layer Measuring Bacterial Growth Fig. 7.13 Fig. 7.14a Plotting growth on graphs Standard Growth Curve  Phases of Growth Lag phase – making new enzymes in response to new medium Log phase – exponential growth –Desired for production of products –Most sensitive to drugs and radiation during this period  Phases of Growth Stationary phase – –nutrients becoming limiting or waste products becoming toxic – death rate = division rate Death phase – death exceeds division  Measuring Growth Direct methods – count individual cells Indirect Methods – measure effects of bacterial growth Fig. i7.6 Fig. 7.17 Turbidity Metabolic Activity Dry Weight