Factors affecting the growth of microorganisms by abilash

The physical factors that affect the growth of Microorganisms

1. Factors affecting the growth of microorganisms By S.Abilash Ist M.Sc Microbiology

2. INTRODUCTION All bacterial and archael cells are haploid. Most reproduce by “binary fission” Binary fission is a relatively simple type of cell division The cell elongates, replicates its chromosome and separates the newly formed DNA molecules Finally septum is formed at the middle of cell dividing the parent cell into two progeny cells.

3. FACTORS AFFECTING MICROBIAL GROWTH Microbes are uptake the nutrients and reproduce, but in some conditions the microbial growth get disturbed. Microorganisms are able to respond to variations in nutrient levels. Microorganisms are greatly affected by the chemical and physical nature of their surroundings.

4. FACTORS Physical factors Chemical Factors

5. Physical Factors Radiation Pulsed electric field (PEF) Pulsed magnetic field (PMF) High power ultrasound Temperature High osmotic gradients High pressure

6. RADIATION Radiation behaves as if it were in water The wave length of EMW decreases with increase in energy Sunlight the major source of radiation Photosynthatic organisms depend on this Sun ray has 60% infra red rays, 3% UV rays

7. Cont..... Different types of UV rays( A,B&C)ranges from longest to shortest Sea level UV Wavelength is about 290nm Below this level it is absorbed by the ozone layer Two types of radiations they are 1 Ionising radiation 2Non-ionising radiation

8. Ionizing Radiation Very short Wavelength and high energy which causes atoms to lose electrons X-rays and gamma rays Low level radiation may cause Mutation High level cause Lethal effect ,i.e. breaks hydrogen bonds, destroys ring structure and polymerizes some molecules Microorganisms are resistant to ionizing radiation e.g. Deinococcus radiodurans which extermely resistant to high ionizing radiation

9. UV radiation Kills microorganisms due to short wavelength (10-400nm) Most lethal wavelength is 290nm absorbed by DNA and damages it However excessive exposure to UV outstrips organisms ability to repair damage

10. UV Resistant Microorgnaisms

11. Visible Light Even visible light at high intensity can kill microbes Pigments called “photosensitizers” & oxygen are involved Photosensitizers absorb light energy and become excited then transfers its energy to oxygen generating singlet oxygen P P (activated) P(activated)+oxygen P +Oxygen Carotenoids convert singlet oxygen into the unexcited state

12. PULSED ELECTRIC FIELDS (PEF) Strong electric field pulses applied to cells cause their membranes to develop pores electroporation increasing membrane permeability with a consequent and for the undesirable migration of chemicals. Pulses of low intensity may result in the increased production of secondary metabolites and a build up of resistance

13. PULSED MAGNETIC FIELDS (PMF) A 2004 study found that E.coli is susceptible to pulsed magnetic fields with a survivability figure of 1 in 10000 Enzymes such as lactoperoxidase , lipase and catalase are readily inactived

14. HIGH POWER ULTRA SOUND Ultrasound generates cavitation bubbles within a liquid or slurry by causing the liquid molecules to vibrate. The process is used for destroying E.coli , Salmonella, Ascaris , Cyanobacterium & polio virus It is also capable of breaking down organic pesticides

15. HIGH POWER ULTRA SOUND

16. HIGH PRESSURE Organisms that spend their lives on land or the surface of water are always subjected to a pressure of 1 atm and are never affected significantly by pressure. High hydrostatic pressures affect membrane fluidity and membrane associated function. Many microbes found at great ocean depths are “ barotolerant ” increased pressure adversely affects them but not as much as it does non tolerant microbes.

17. PIEZOPHILIC MICROBES They grow more rapidly at high pressure A piezophile is defined as an organism that has a maximal growth rate at pressures greater than 1atm but less than about 590atm An important adaptation observed in piezophiles is that they change their membrane lipids in response to increasing pressure. Eg: Photobacterium , Shewanella

18. Temperature

19. Temperature

20. Temperature Microorganisms are particularly susceptible to external temperatures because they cannot regulate their internal temperature. High temperature denature enzymes, transport carriers and other proteins. Temperature also has a significant effect on microbial membranes. Low - membrane solidify High - the lipid bilayer simply melts & disintegrates

21. Based on the temperature range microbes are classified into Psycrophiles Psycrotolarent Mesophiles Thermophiles Hyperthermophiles Extermethermophiles

22. Psycrophiles It grow well at 0°C and have an optimum growth temperatures of 15°C ; the maximum is around 20°C. Eg : Pseudomonas, Vibrio , Bacillus, Shewanella etc. Many psychrophiles begin to leak cellular constituents at temperature higher than 20°C because of cell membrane disruption Psycrophiles

23. Cold active enzyme It is a holoenzyme with high amount of Alpha helix and low amount of beta sheets Has greater polar ends and lesser hydrophobic end The cytoplasm of psycrophiles have high amount of unsaturated fattty acid E.g. Psychroflexus sp has fatty acids with 4-5 double bond molecules

24. Psycrotolarent Can grow at 0C but it has optimal temperature of 25c and maxima at 35c E.g. Psychrophilic algae Which produce characteristic colour due to the presence of pigment e.g. Chlamydomonas nivalis It has red colour pigment production It multiplies when the ice starts melting

25. Mesophiles These are microorganisms that grow in moderate temperatures. They have growth optima around 20 – 45 °C and often have a temperature minimum of 15 – 20 °C and a maximum of about 45°C They are common flora which infection to the humans E.g. E.coli

26. Mesophiles

27. Thermophiles Grow at temperatures between 55 and 85°C. Their growth minimum is around 45°C Eg: Thermoplasma acidophilum

28. Hyperthermophiles It have growth optima between 85°C & about 113°C. They usually do not grow below 55°C. Eg: Pyrococcous abyssi Hot springs (150-500c) Hydrothermal vents 350c

29. SOLUTE AND WATER ACTIVITY Because a selectively permeable plasma membrane separates microorganisms from their environment, they can be affected by changes in osmotic concentration of their surroundings If a microorganism is placed in hypotonic solution (lower osmotic concentration) water will enter the cell and cause it to burst. If it is placed in a hypertonic solution (higher osmotic concentration) water will flow out of the cell.

30. Cont.... In microbes that have cell walls the membrane shrinks away from the cellwall a process called “ plasmolysis ”. Dehydration of the cell in hypertonic environments may damage the cell membrane cause the cell to become metabolically inactive. Microbes be able to respond to changes in the osmotic concentrations of their environment.

31. HALOPHILES It require the presence of Nacl or other salts at the concentration above about 0.2M. “extreme halophiles ” have adapted so completely to hypertonic saline conditions that they require high levels of Nacl to grow. Eg: Halobacterium It can be accumulate enormous quantities of potassium and chloride ions

32. Types of Halophiles Mild Halophiles (1-6% NaCl ) Moderate Halophiles (7-15% NaCl ) Exterme Halophiles (15-30%)

33. OXYGEN CONCENTRATION

34. Oxygen requirement Group Relationship Type of metabolism Example Habitat Aerobes Obligate Required Aerobic respiration Micrococcus luctes Skin,dust Facultative Not required but growth better with oxygen Aerobic &Anaerobic E.coli Large intestine Microarophiles Required lower than atmospheric Aerobic Spirillum volutus Lake water Anaerobe Aerotolarent Not required but no better growth with oxygen Fermentation Streptococcus pyogens Upper respiratory tract Obligate Harmful or lethal Methanobacterium formicium Anoxic lake sediments

35. An organism able to grow in the presence of atmospheric oxygen is an aerobe; where as one that grow in its absence is an anaerobe. Almost all multicellular organisms are completely dependent on atmospheric O2 for growth that is they are obligate aerobes. Microaerphiles such as Campylobacter are damaged by the normal atmospheric level of O2 (20%) they require only (2 – 10%) for growth.

36. Facultative anaerobes do not require O2 for growth but grow better in its presence. Aerotolerant anaerobes such as Enterococcus faecalis grow equally well whether O2 is present or not. Obligate anaerobes are usually killed in the presence of O2. Eg: Methanococcus , Clostridium pasteurianum

37. A microbial group may show more than one type of relationship to O2. The different relationships with O2 are due to several factors including the “inactivation of proteins and the effect of toxic O2 derivatives” Enzymes can be inactivated when sensitive groups are oxidized. Eg : The nitrogen fixation enzyme nitrogenase which is very oxygen sensitive

38. Prevention from oxygen attack Oxygen present in the environment sometime s may lyse the bacterial cell Catalase H2O2+H2O2 2H2O+O2 Peroxidase H2O2+NADH+H 2H2O+NAD Superoxide dimutase O2+O2+2H H2O2+O2

39. Cont... Superoxide dimutase / Catalase incombination 4O2+4h 2H2O+3O2 Superoxide reductase O2+2H+Cyt C H2O2+Cyt C

40. PH

41. PH PH is a measure of the relative acidity of a solution and is defined as the negative logarithm of the hydrogen ion concentration. Each species has a definite PH growth range and PH growth optimum. Acidophiles – optimum PH 0 and 5.5 Neutrophiles – optimum PH 5.5 and 8.0 Alkaliphiles - optimum PH 8.0 and 11.5

42. ACIDOPHILES E.g. Acidithiobacillus sp, sulfolobus sp, Thermoplasma sp, Feroplasma sp Ph raised cytoplasm destroyed indicating that high concentration of H ions needed for membrane stability

43. Alkaliphiles Alkali loving, need high concentration of alkali and high carbonate solution Some species of this range have board range E.g Bacillus flemus has a range between 7.5- 11

44. Neutrophiles Lives at ambient ph around 7 Most of the beneficial and harmful bacteria live at this ph Hence is the reason for so many microbial infection in the human health E.g E.coli

45. Chemical factors Nutrition type Nutrition needed

46. OPEN SESSION ?

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