Chapter 8 - Energy sourses, nutritional types, and growth media

Composition of bacteria by major polymers

% of total dry weight of cells

• 3% DNA

• 21% RNA

• 55% protein

• 3.5%peptidoglycan

• 9% phospholipid

• 3.5% lipopolysaccharide

this data is likely from e. coli @ 37*C, etc.

what makes up most of the weight of bacteria ?

proteins

fungi and bacteria

fungi aid bacteria by breaking down polymers and isomerizing? them into other polymers

Nutritional types

defined by energy, carbon, and hydrogen/electron (H/e-) source

which classes of bacteria use energy sources, carbon sources, and H/e- sources

• Energy sources

  • used by phototrophs and chemotrophs

• Carbon sources

  • used by autotroph heterotrophs

• H/e- sources

  • used by lithotrophs and organotrophs

phototrophs vs. chemotrophs

• phototrophs - bacteria which can use sunlight

• chemotrophs - bacteria that oxidise organic or inorganic compounds

autotrophs vs. heterotrophs

• autotrophs - bacteria reduce CO2 to CHX

• heterotroph - obtain carbon from reduced organic compounds (NOT CO2)

lithotrophs vs. organotrophs

• lithotrophs - use reduced inorganic compounds as H/e- source

• organotrophs - use organic compounds as H/e- source

  • pull electrons (oxidize) organic compounds

4 main classes that bacteria fall into

• Chemolithotrophic autotrophs

• photoorganotrophic heterortrophs

• photolithotrophic autotrophs

• chemoorganic heterotrophs

chemolithotrophic autotrophs

• ex. Thiobacillus

• Fe+2 > Fe+3 + e-, CO2

photolithotrophic autotrophs

cyanobacteria

• plant-like photosynthesis

• fix atmospheric CO2

photolithotrophic autotrophs

cyanobacteria

• plant-like photosynthesis

• fix atmospheric CO2

chemoorganic heterotophs

chemoheterotrophs and heterotrophs

• E. coli, pathogens, degraders

calvin cycle

autotrophic fixation of CO2

• energy consuming process

• mostly restricted to photosynthetic bacteria

• oxygenic photosynthesis like that of higher plants

• performed by cyanobacteria

Other carbon sources

• the reverse TCA cycle

  • succinyl-CoA + CO2 > a-ketoglutarate

  • a-ketoglutarate + CO2 > isocitrate

• methanogenesis

  • CO2 binds to a CH3-carrier

  • some fixed carbon is diverted to producing cellular carbon

  • both an energy producing and carbon fixing process

heterotrophic carbon sources

• carbohydrates

  • simple sugars, amino sugars, sugar acids

  • amino acids

  • alcohols, hydrocarbons

  • organic acids

    • citric, lactic, acetic, succinic acids

nitrogen

usually the growth-limiting nutrient in any environment

• organic nitrogen is usually reduced to the level of the amino group NH3 (N-3)

• most nitrogen on Earth is atmospheric N2 gas

  • must be fixed or reduced to be biologically useful

4 Sources of Nitrogen

1. most nitrogen on Earth is atmospheric N2 gas

• must be fixed or reduced to be biologically useful

2. provided as growth media as a nitrate or ammonium salt

• KNO3, NH4NO3

• NO3 or NO2 is reduced to NH3 by many bacteria

  • NH3 is then assimilated into cellular material

  • NH3 → glutamate → glutamine

3. provided as organic compounds like amino acid or urea

• protein hydrolysate like tryptic soya

4. through preformed amino acids and N containing bases

which organisms can naturally fix N2

ONLY BACTERIA can naturally fix N2

• free living bacteria

  • ex. Cyanobacteria, Klebsiella

• symbiotic bacteria

  • ex. Rhizobium

phosphorus

may also be limiting nutrient

• organic phosphorus is the major source of phosphorus for bacteria

  • DNA, RNA, nucleotides

  • phospholipids

• provided in growth media as phosphate salt

  • ex. Na2HPO4

Sulphur source

• Inorganic sulphur

  • SO4-2 salts which are taken up by the cell and reduced to SH2 level

• Organic sulphur

  • cysteine

  • methionine