Growth & nutrition of bacteria

Microbiology
1st year bsc nusring topic

1. Growth & nutrition of bacteria - Ms. Khyati Chaudhari

2. Introduction Growth is an orderly increase in the quality of cellular constituents. For most bacteria, growth involves increase in cell mass and duplication of the bacterial DNA, synthesis of new cell wall and cellular membrane, and finally cell division. This asexual process of reproductive called binary fission. One bacterial cell divides into two cells, two cells into four, and so on. For such biosynthesis every organism requires substances that must be present in their environment. Such substances of environment utilized for growth of an organism are referred to as nutrients.

3. Growth Requirements Various requirement for bacterial growth are; Major elements: These include C, H, O, N, S, P, K, Mg, Fe, Ca, Mn and traces of Zn, Cu, Co, and Mo. These elements are found in the form of water, inorganic ions, small molecules and macromolecules which serve either a structural or functional role in the cells. The general physiological functions of the elements are outlined in the following table;

4. Growth Requirements Major elements, their sources and functions in bacterial cells. ELEMENTS DRY WT % SOURCE FUNCTIONS CARBON 50 Organic Compounds or CO 2 Main constituent of cellular material. OXYGEN 20 H 2 O, Organic compounds, CO 2 & O 2 Constituent of cell material and cell water, electron acceptor in aerobic respiration. NITROGEN 14 NH 3 , NO 3 , Organic compounds, N 2 Constituent of amino acids, nucleic acids, nucleotides and coenzymes.

5. ELEMENTS DRY WT % SOURCE FUNCTIONS HYDROGEN 8 H 2 0, Organic compounds, H 2 Main constituent of organic compounds and cell water. PHOSPHORUS 3 Inorganic phosphates (PO 4 ) Constituent of nucleic acids, nucleotides, phospholipids, LPS, teichoic acids. SULFUR 1 SO 4 , H 2 S,SO 2 , Organic sulfur compounds Constituent of cysteine, methionine, glutathione, several coenzymes. POTASSIUM 1 Potassium salts Main cellular inorganic cation and cofactor for certain enzymes.

6. ELEMENTS DRY WT % SOURCE FUNCTIONS MAGNESIUM 0.5 Magnesium Salts Inorganic cellular cation, cofactor for certain enzyme reaction. CALCIUM 0.5 Calcium Salts Inorganic cellular cation, cofactor for certain enzymes and a component of endospores. IRON 0.2 Iron Salts Component of cytochromes and certain non-heme iron-proteins and a cofactor for some enzymatic reactions

7. Growth Requirements These are the elements which are required in such small amounts that they are present as “contaminants” of the water or other media components. The trace elements usually act as cofactors for essential enzymatic reactions in the cell. One organism’s trace element may be another’s required element and vice-versa and include Mn, Cu, Co and Mo.

8. Growth Factors An organism, whether it is an autotroph or a heterotroph, may require small amount of certain organic compounds for growth, such compounds are called growth factors. Growth factors are required in small amounts by cells because they fulfill specific in biosynthesis. Growth factors are organized into three categories. Purines & Pyrimidines: required for synthesis of nucleic acids(DNA & RNA). Amino acids: required for synthesis of proteins. Vitamins: Vitamins are needed as coenzymes and functional groups of certain enzymes.

9. Nutritional types of bacteria: On the basis of carbon & energy sources for growth, bacteria are broadly divided into two groups: Autotrophic Bacteria The bacteria which are able to synthesize their own organic food from inorganic substances supplied from environment are called autotrophic bacteria and thus mode of nutrition as autotrophy or autotrophic nutrition. These bacteria can be divided further into two types as follows: Photoautotrophic Bacteria Chemoautotrophs or Chemosynthetic Bacteria

10. CONT… PHOTOAUTOTROPHIC BACTERIA T hese bacteria utilize solar energy to synthesize their organic metabolites as they possess photosynthetic pigments in membrane bound lamellae or thylakoids. Ex. P urple bacteria CHEMOAUTOTROPHS These are non-photosynthetic bacteria which manufacture organic compounds from inorganic raw materials & utilize energy liberated from the oxidation of these inorganic substances. Ex. Nitrogen fixing bacteria

11. CONT… Heterotrophic Bacteria The bacteria which are unable to manufacture their own organic food & hence are dependent on external source are called heterotrophs and the mode of nutrition as heterotrophy or heterotrophic nutrition. These bacteria can be further divided into two groups: Photo heterotrophs Chemo heterotrophs

12. CONT… PHOTO HETEROTROPHS They are considered to be intermediate between photoautotroph’s and chemo heterotrophs because they posses unique feature of utilizing light energy(like photoautotrophs) in synthesizing their food from organic raw materials absorbed from environment. They therefore, do not use inorganic raw materials to synthesize their food. Ex. Dokdonia

13. CONT… CHEMO HETEROTROPHS Majority of heterotrophic microorganisms belong to this category. Since they can not synthesize their own food (organic substances), they obtain it directly from external environment using organic compounds . Ex. Sulfur bacteria

14. CONT… NUTRITIONAL TYPE ENERGY SOURCE CARBON SOURCE Photoautotrophs Light CO 2 Photo heterotrophs Light Organic compounds Chemoautotrophs Inorganic compounds, e.g. H 2 , NH 3 , NO 2 , H 2 S CO 2 Chemo heterotrophs Organic compounds Organic compounds

15. CONT… Saprophytic Bacteria: These bacteria obtain their nutritional requirements from dead organic matter. They breakdown the complex organic matter into simple soluble form. They absorb the simple nutrients & assimilate them, during which they release energy. These bacteria have a significant role in the ecosystem functioning as decomposers . Symbiotic Bacteria: These are bacteria which live in a mutually beneficial association with other organisms. Such bacteria derive the essential nutrients from their host organisms and in that process help the host through some of their biological activities.

16. CONT… e.g. Escherichia coli found in the human alimentary canal checks the growth of harmful putrefying bacteria, release vitamin K and B 12 which are necessary for blood components. Parasitic Bacteria: These are bacteria which occur in the body of animals and plants, obtaining their organic food from them. Most of these bacteria are pathogenic, causing serious disease in the host organisms . Ex., streptococcus , staphylococcus, Salmonella, mycoplasma etc .

17. Culture Media for Growth of Bacteria The consistent growth and survival of microorganisms depend on an adequate supply nutrients and favorable environmental conditions in which growth is supported. To fulfill these conditions, microorganisms must use soluble, low molecular weight substances derived frequently from enzymatic degradation of complex nutrients. A solution containing these nutrients so prepared directly used for growth and multiplication of microorganisms is referred as “ C ulture Medium”. Definition- The food material or substance required for growing micro organisms in vitro (outside the body) is called culture medium.

18. Types of Culture Media Media has been classified in many ways: Simple media (Basal media) Complex media Synthetic media ( D efined media) Enriched media Selective media Indicator media

19. Types of Culture Media Differential media Sugar media Transport media Anaerobic media

20. Simple Media A simple medium like nutrient broth consist of peptone, meat extract, sodium chloride, and water. Nutrient agar made by adding 2% agar to nutrient broth is the simplest and most common in routine diagnostic laboratories. These media support growth of most bacteria. Examples : Nutrient broth = peptone water ( 1% peptone + 0.5 % NaCl + 100 ml water) + 1% meat extract Uses : To grow non fastidious micro organism

21. Complex Media These media has additional special ingredients that are required for the growth of or for bringing out certain characteristics of certain bacteria. In simple term, media that contain some ingredients of unknown chemical composition are complex media. Uses : To cultivate all the fastidious organisms

22. Synthetic Media These media are prepared from pure chemical substances and the exact composition of the medium is known. Typically, they contain a simple sugar as the carbon and energy source, an inorganic nitrogen source, various mineral salts and if necessary growth factors. ( i.e. Purified amino acids, vitamins, purines and pyrimidines.)

23. Enriched Media In these media, substances such as blood, serum or egg are added to a basal medium. They are used to grow bacteria which are more fastidious in their nutritional needs. Examples: blood agar, chocolate agar and egg containing media E nriched media is always a solid media.

24. Enriched Liquid Media Enrichment media are liquid media into which certain substances are added which inhibit a growth of some bacteria and selectively stimulate the growth of others are called enrichment media. Ex. Stool cultures, the non pathogenic or commensal bacteria, will normally overgrow V ibrio Cholerae. However, if alkaline peptone water is used for the culture, this inhibits the commensal bacteria and allows the Vibrio Cholerae to grow. Commensal bacteria : living in a relationship in which one organism derives food or benefits from another organism without hurting or helping it.

25. Selective Media Serve the same purpose as enrichment media but are solid in consistency. Into which certain substances are added which inhibit other bacteria and that help select the organism of interest. Ex. Thiosulphate Citrate Bile Salt Sucrose agar (TCBS) medium for Vibrio Cholerae. Uses: to cultivate salmonella, shigella & mycobacteria.

26. Indicator Media These media contain an indicator that changes color when a particular kind of bacterium grows on them. An example is the incorporation of sucrose in TCBS media. Vibrio Cholerae ferments sucrose and so appears yellow colonies on the medium. Fermentation : the chemical breakdown of substance by bacteria, yeasts or other micro-organisms

27. Differential Media A medium that has special substances added to it which help to bring out differing characteristics of bacteria and thus help to distinguish between them is a differential media. Ex. MacConkey’s medium which shows up lactose fermenters as pink colonies, while non-lactose fermenters are colorless or pale . This may also be termed as an indicator medium.

28. Sugar Media The term sugar in microbiology denotes any fermentable substance. They may be : Monosaccharides, ex. Dextrose & mannose Disaccharides, ex. Sucrose & lactose Polysaccharides, ex. Starch, insulin Trisaccharides, ex. Raffinose Alcohols, ex. Glycerol & sorbitol Glucosides, ex. Salicin & esculin

29. Sugar Media The usual sugar media consist of 1% sugar in peptone water along with an indicator. A small tube( Durham's tube) is kept inverted in the sugar tube to detect gas production.

30. Transport Media Transport media are used when specimens might contain delicate organisms (ex. Neisseria Gonorrhea ) Which may not survive the time taken for transport to the laboratory. Secondly, transport media can be used when pathogens may be overgrown by the non-pathogen. Ex. Stuart’s medium for Neisseria Gonorrhea & buffered glycerol saline for Shigella species.

31. Anaerobic Media The media is used to grow anaerobic organisms. E x. Robertson’s cooked meat medium and thioglycollate medium.