Orderly increase in all the chemical structures of the cell. Cell multiplication. Increase in the number of the cells

Transcription

1 GROWTH OF BACTERIA

2 Growth Orderly increase in all the chemical structures of the cell Cell multiplication Increase in the number of the cells In natural habitat In or on another organism (infection) In laboratory (bacterial culture)

3 Binary fission

4 Binary fission

5 Growth rate The number of doubling per hour The number of cells in new generation is double of the cells in previous generation The population size increases at an exponential rate during active growth

6 Generation time (doubling time) The time required for one cell to divide into two cells e.g. 20 mns for Escherichia coli 24 hrs for Mycobacterium tuberculosis

7 Calculation of the number of bacteria B f = B i x 2 n B f = Final number of bacteria B i = Initial number of bacteria N= Number of generations N= Total amount of time/ Generation time

8 Growth curve for bacteria A- The lag phase: Adaptation period

9 Growth curve for bacteria B-The acceleration phase: Start to grow

10 Growth curve for bacteria C- The exponential phase: Logarithmic growth

11 Growth curve for bacteria D-The retardation phase : Growth rate begins to decrease

12 Growth curve for bacteria E- The maximum stationary phase: Viable cell count stays constant (death=growth)

13 Growth curve for bacteria F- The death phase : Death rate increases, viable cell count decreases

14 Requirments for growth Nutrients Environmental conditions Source of energy

15 Nutrients Carbon source: Carbon is required for all functions of bacteria Autotrophs : Able to grow simply, using inorganic carbon in the form of mostly carbon dioxide as their sole source of carbon Heterotrophs : Require an organic carbon source (mostly carbohydrates). Obtain their energy by Fermenting Oxidazing Organic compounds

16 Classification according to predominant source of carbon

17 Nutrients Nitrogen source: Major component of proteins and nucleic acids. Most of the bacteria use ammonium salts, organic acids, aminoacids as nitrogen source through assimilation reduce nitrate(no 3- ) and nitrite (NO 2- ) form ammonium ion (NH 4+ ) as end product

18 Nutrients Sulfur source: Sulfur forms part of the structure of coenzymes, and found in cysteinyl and methionyl side chains of proteins. Microorganisms mostly use sulfate (SO 4 ) as sulfur source end product is hydrogen sulfide (H 2 S).

19 Nutrients Phosphorus source: Phosphate (PO 4 ) is required as a component of ATP, nucleic acids, coenzymes. Phosphate is always assimilated as free inorganic phosphate (P)

20 Nutrients Mineral sources: Minerals are required for enzyme functions, ribosomes, cell wall integrity, etc. Mg, Ca, K, Na,Fe, Mn, Mo, Co, Cu, Zn are some of the minerals that many organisms need for their growth.

21 Nutrients Growth factors: A growth factor is an organic compound which is required for growth of bacteria but can not be synthesized by them Some species require more than 20 growth factors for growth.

22 Requirments for growth Nutrients Environmental conditions Source of energy

23 Environmental factors Hydrogen ion concentration (ph): Neutrophiles*: grow best at ph: (opt ph: ) Acidophiles: grow best below ph:5.5 (down to ph:3) Alkalophiles: grow best above ph:9 (up to ph: )

24 Environmental factors Temperature: Psychrophilic: 10 o -20 o C Mesophilic*: 20 o -40 o C (optimal 35 o -37 o C) Thermophilic: 50 o -60 o C All human pathogens are mesophiles.

25 Environmental factors Growth atmosphere Oxygen requirement: Obligate aerobes Obligate anaerobes Facultative anaerobes Microaerophiles Carbon dioxide requirement: Capnophiles (5-10% carbondioxide)

26 Environmental factors Ionic strength and osmotic pressure: Most bacteria are able to tolerate wide range of external osmotic pressures and ionic strengths by active transport systems Osmophilic: Organisms which need normal osmotic pressures for growth Halophilic: Organisms which need high salt concentration for growth (marine organisms)

27 Requirments for growth Nutrients Environmental conditions Source of energy

28 Source of energy ATP Fermentation Respiration Photosynthesis (phototrophic organisms)

29 Cultivation Cultivation is the process of growth of microorganisms in laboratories. Nutritional conditions Environmental conditions

30 Nutritional conditions For cultivation of bacteria laboratory growth media are used: Liquid media (in tubes) Solid media (in plates or tubes)- 1.5%-3% agar Semi-solid media (in tubes) 0.3%-0.5% agar

31 Laboratory media Liquid media in tube

32 Laboratory media Solid media in tubes

33 Laboratory media Solid media in plate

34 Classification of laboratory media based on usage purposes Basic media: Contain basic nutritional requirements (e.g. Nutrient agar, nutrient broth) Enriched media: Basic media + enrichment with blood, serum, etc. (e.g. Blood agar, chocolate agar)

35 Nutrient Agar Blood Agar AHMET PINAR, M.D., Ph.D. Choclate Agar

36 Classification of laboratory media based on usage purposes Selective media: Used to grow a particular group of microorganisms while inhibiting others (eg. EMB agar, antibiotic added media) Differential media: Used to distinguish a particular group of microorganisms from others (eg. Mac Conkey agar ) AHMET PINAR, M.D., Ph.D.

37 Mac Conkey Agar

38 Classification of laboratory media based on usage purposes Identification media : Used to identify the type of microorganisms according to their biochemical properties (eg. fermentation medium, citrate medium, TSI medium) Fermentation Medium

39 Citrate Medium TSI Medium

40 Classification of laboratory media based on usage purposes Special media: Used for the growth of certain bacteria (eg. Löwenstein-Jensen medium, Loeffler medium) Transport media: Stuart, Carry-Blair

41 Environmental conditions ph of media, moist, heat, temperature. İncubators C hrs

42 Detection of growth in laboratories Turbidity in liquid media Colonies on solid media

43 Growth in liquid medium

44 Growth in liquid medium

45 Decreasing the number of bacteria with quadrant streak method. Single colonies

46 Growth on solid medium

47 S=Smooth R= Rough M=Mucoid Colony types