MICROBIAL NUTRITION

Essential Nutrients

Chemical Composition of a Prokaryotic Cell

Component % Total Cell WeightWater 70

Inorganic ions 1

Sugars & precursors 3

Amino acids & precursors 0.4

Nucleotides & precursors 0.4

Lipids & precursors 2

Other small molecules 0.2

Macromolecules (proteins,nucleic acids & polysaccharides)

22

CATEGORIZATION

• Essential Nutrients: C H N O P S - common requirements

MACRONUTRIENTS/MACROELEMENTS

Required in large quantities

Play principle roles in cell structure, metabolism

PROTEIN

CH2O

LIPIDS

NUCLEIC ACIDS

• 4 remaining: POTASSIUM (enzymes, protein synthesis)

CALCIUM (heat resistance, other function)

MAGNESIUM (cofactor for enzymes)

IRON (cytochromes)

Exist in cell as cations, various roles

• MICRONUTRIENTS/TRACE ELEMENTS

MANGANESE

ZINC

NICKEL

COBALT

COPPER

MOLYBEDNUM

Required in small quantities, role in enzyme function, maintenance of protein structure

CARBON CONTENT

• INORGANIC NUTRIENTS

Simple atom or molec

Combined with other atoms (NOT C or H)

e.g., Metals/metal salts:

Magnesium sulphate, ferric nitrate

Gases: Oxygen

• ORGANIC NUTRIENTS

Contain C and H atoms

Range SIMPLE (CH4, methane) POLYMERS (CH2O’s, lipids etc)

SOURCES OF ESSENTIAL NUTRIENTSRequirements For CARBON, HYDROGEN & OXYGEN

Elements/nutrients exist in inorganic reservoir

• CARBON• HETEROTROPHS - from organic matter

(bodies of other org’s - dependant on other life forms)

used in PROTEINS, CH2O’s, LIPIDS & NUCLEIC ACIDS

Most common source - sugars, i.e., GLUCOSE

• AUTOTROPHS - from inorganic CO2 (gas)

(ability to convert CO2 Organic compds - NOT dependant on living forms)

Used in INTRACELLULAR STRUCTURE & METABOLISM

• NITROGEN

Usually supplied via inorganic molec

I.e., NH3, NO3, some use NO2 (nitrite), N2 (gas)

**IMPORTANT all inorganic forms are 1st converted to NH3

AMMONIA

NH3

NITROGEN GASN2

NITRITENO2 AMINO ACID

FORMATION

AMINOACIDS

PROTEIN

NITRATENO3

NITROGEN CYCLE Nitrobacter sp., Nitrosomonas sp., Rhizobium sp.

• NOTE N2 gas - found in org’s, soil & water

NITROGEN FIXATION - take up gas, add hydrogens

Mainly soil microorganisms

Few infectious microbes

e.g., Klebsiella when other sources absent

Used in STRUCTURE OF PROTEINS, DNA, RNA, ATP

• HYDROGEN

Organic compd’s, H2O, salt H3PO4, gas H2S, CH4, H2

Used in MAINTENANCE OF pH, HYDROGEN BONDING, OXIDATION-REDUCTION REACTIONS

• PHOSPHORUS (PHOSPHATE)

Inorganic source PO4-3 from H3PO4

Used in SYNTHESIS of NUCLEIC ACIDS, ATP, BUFFER of pH

• SULPHUR

Inorganic SO4-2, FeS, H2S, elemental S

Used in FORMATION of certain Aa’s; cysteine, methionine, SOME VITAMINS, PROTEIN STABILITY & SHAPE

SULPHUR CYCLEThiobacillius sp., Beggiatoa sp., Sulfofobus sp.

MINERALS

ELEMENT

MAGNESIUM

POTASSIUM

IRON

FUNCTION

Stabilization of nucleic acids, some

ribosomes, enzymatic reaction

Some enzymatic reactions -

protein synthesis

Component of CYTOCHROMES,

diphtheria toxin prodn

Corynebacterium diphtheriae

ELEMENT

CALCIUM

ZINC

MOLBDENUM

COBALT

MANGANESE

SODIUM

FUNCTION

Cofactor some enzymes, required

for attachment of some bacterial

viruses to bacterial cells, spore

formation

Cofactor some enzymes

Component of enzymes involved

in N2 fixation

Component of Vitamin B12

Can substitute for magnesium

Required 1o for marine microbes

NUTRITIONAL TYPES

Determined by CARBON & ENERGY SOURCES

• AUTOTROPHS

Energy from 1 of 2 non-living sources

SUNLIGHT (PHOTOAUTOTROPHS)

Process of PHOSYNTHESIS

CO2 + H2O (CH2O)n + O2

e.g. plants, algae, Cyanobacteria

CHEMICAL REACTION (CHEMOAUTOTROPHS)

SIMPLE INORGANIC (LITHOTROPHS)

Process of METHANOGENESIS

4 H2 + CO2 CH4 + 2 H2O

e.g. Methanogens: Methanosarcina, Methanobacterium

• HETEROTROPHS

Majority CHEMOHETEROTROPHS/CHEMOORGANOTROPHS

BOTH carbon + energy from ORGANIC COMPD’S

Process of RESPIRATION or FERMENTATION

[(CH2O)n] + O2 CO2 + H2O + ATP

• 2 CATEGORIES OF MICROBES:

SAPROBES & PARASITES

• SAPROBIC

Decomposers of plant litter, animal matter, dead org’s

“NATURAL RECYCLERS”

Decomposers of matter that would build up

OBLIGATE SAPROBES

Exists entirely organic matter

Unable to adapt to host body

e.g. Most free-living; Protozoa, Fungi

FACULTATIVE SAPROBES

Infects a host

Normally host is compromised

“OPPOTUNISTIC PATHOGEN”

e.g. Pseudomonas aeruginosa (Hospitalized patients

Cryptococcus neoformans (AIDS patients)

• PARASITIC

Live in or on body of host

Usually harm host

e.g. Viruses, Helminth worms

PATHOGENS

Cause damage to tissues death

e.g. HIV (AIDS)

OBLIGATE PARASITES

Unable to grow outside host

e.g. Leprosy bacillus, syphilis spirochete

SUMMARYCATEGORY CARBON ENERGY EXAMPLE

AUTOTROPHIC CO2 NON LIVING SELF-FEEDER

1. PHOTOAUTOTROPH CO2 SUNLIGHT ALGAE, PLANTCYANOBACTERIA

CHEMIAUTOTROPH CO2 SIMPLEINORGANIC

COMPS

METHANOGEN

HETEROTROPHIC ORGANIC OTHERORG’S ORSUNLIGHT

OTHER-FEEDER

1.PHOTOHETEROTROPH

ORGANIC SUNLIGHT NON-SULPHURBACTERIA

2.CHEMOHETEROTROPH

ORGANIC METABOLICCONVERSION

PROTOZOA,FUNGI,

BACTERIA,ANIMALS

GROWTH FACTORS

• Organic compounds required as essential cell components or precursors

• CANNOT be synthesized

• 3 major classes:

Amino acids (protein synthesis)

Purines & Pyrimidines (nucleic acid synthesis)

Vitamins (all or part of enzymes cofactors)

Enterococcus faecalis (lactic acid bacterium) requires 8 vitamins for growth

TRANSPORT MECHANISMS

• Required for NUTRIENT UPTAKE & ABSORPTION

3 Types:PASSIVE TRANSPORT

ACTIVE TRANSPORT

BULK TRANSPORT

• PASSIVE TRANSPORT

Requires no energy input

Atomic/molec movement

2 Types:DIFFUSION

OSMOSIS

DIFFUSION

Molec movement from area of high [ ] to low [ ]

Method cells obtain freely diffusible materials

e.g. O2, CO2, H2O

Also release waste products from cell

OSMOSIS

Diffusion of water through selectively permeable membrane

Openings in membrane allow free flow of water BUT blocks other molec’s

OSMOTIC RELATIONSHIPS IN LIVING SYSTEMS

ISOTONIC

HYPOTONIC HYPERTONIC

ISOTONIC

Environment in equal [ ] to cell internal environment

NO NET CHANGE IN CELL VOLUME

HYPOTONIC

[Solute] of external environment lower than cell internal environment

(PURE WATER) most HYPOTONIC FLUID

Flow of water INTO cell

Protoplast swells, pushes against cell wall

Cell wall prevents bursting

HYPERTONIC

Environment has higher [Solute] than cell internal structure

Flow of water OUT of cell

NB Soln’s LETHAL to microbes (salt water, sugar soln’s)

Water diffuses out of cell, shrinks protoplast (PLASMOLYSIS)

• ACTIVE TRANSPORT

Brings nutrients INTO cell against gradient

ENSURES CONSTANT SUPPLY OF NUTRIENTS

Features:

1) Nutrients transported against diffusion gradient or in the same direction BUT at a faster rate

2) Presence of specific membrane proteins

(PERMEASES + PUMPS)

3) Expenditure of energy

SUBSTANCES TRANSPORTED:monosacc’s, Aa’s, organic acids, phosphates, metal ions

• BULK TRANSPORT

Transport of larger molec’s, particles, liquids across cell membrane

DO NOT PASS THROUGH

Process ENDOCYTOSIS

PHAGOCYTOSIS

Engulfment followed by vacuole formation (vesicle)

e.g. Amoeba

PINOCYTOSIS

Engulfment of liquids into cell