A Microbial Nutrition Week

Microbial nutrition I’m Staphylococcus aureus

And I’m Streptococcus agalactiae

Nutrient Requirements

Energy Source 

Phototroph 



Uses light as an energy source

Chemotroph 

Uses energy from the oxidation of reduced chemical compounds

Electron (Reduction potential) Source 

Organotroph 



Uses reduced organic compounds as a source for reduction potential

Lithotroph 

Uses reduced inorganic compounds as a source for reduction potential

Carbon source 

Autotroph 



Can use CO2 as a sole carbon source (Carbon fixation)

Heterotroph 

Requires an organic carbon source; cannot use CO2 as a carbon source

Nitrogen source 

Organic nitrogen 



Oxidized forms of inorganic nitrogen 



Nitrate (NO32-) and nitrite (NO2-)

Reduced inorganic nitrogen 



Primarily from the catabolism of amino acids

Ammonium (NH4+)

Dissolved nitrogen gas (N2) (Nitrogen fixation)



Phosphate source  

Organic phosphate Inorganic phosphate (H2PO4- and HPO42-)

Sulfur source  

Organic sulfur Oxidized inorganic sulfur 



Reduced inorganic sulfur 



Sulfate (SO42-) Sulfide (S2- or H2S)

Elemental sulfur (So)

Special requirements   

Amino acids Nucleotide bases Enzymatic cofactors or “vitamins”

What are the factors that Influenced the growth of bacteria?? Hmmm…

I’m streptococcus pyogenes

Oxygen requirements 

Aerobes  



Anaerobe  



Obligate facultative Obligate facultative

microaerophillic

Thermal requirement 

Cryophillic or Psychrophiles 



Mesophillic 



Optimum around 20 – 45ºC

Thermophillic 



Grows well at 0ºC; optimally between 0ºC – 15ºC

Optimum around 55 – 65 ºC

Thermoduric 

Optimum around 80 – 113 ºC

pH requirement 

Acidophillic 



Basophillic/alkalophiles 



Grow optimally between ~pH 0 and 5.5 Grow optimally between pH 8 – 11.5

Neutrophiles 

Grow optimally between pH 5.5 and 8

Salt concentration 



Halophiles require elevated salt concentrations to grow; often require 0.2 M ionic strength or greater and may some may grow at 1 M or greater; example, Halobacterium Osmotolerant (halotolerant) organisms grow over a wide range of salt concentrations or ionic strengths; for example, Staphylococcus aureus

Growth in Batch Culture

Microbial genetics

Structure and Function of Genetic Material 

DNA & RNA   

DNA=deoxyribonucleic acid RNA=ribonucleic acid Basic building blocks:  Nucleotides  Phosphate group  Pentose sugar  Nitrogenous base

Structure of DNA    

Double stranded (double helix) Chains of nucleotides 5’ to 3’ (strands are anti-parallel) Complimentary base pairing  

A-T G-C

DNA Structure Phosphate-P Sugar-blue Bases-ATGC

DNA Replication  



Bacteria have closed, circular DNA Genome: genetic material in an organism E. coli  



4 million base pairs 1 mm long (over 1000 times larger that actual bacterial cell) DNA takes up around 10% of cell volume

Protein Synthesis 

DNA------- mRNA------ protein transcription

translation

Central Dogma of Molecular Genetics

Transcription 





One strand of DNA used as a template to make a complimentary strand of mRNA Promoter/RNA polymerase/termination site/5’ to 3’ Ways in which RNA & DNA differ:   

RNA is ss RNA sugar is ribose Base pairing-A-U

Transcription

Types of RNA 

Three types: 





mRNA: messenger RNA  Contains 3 bases ( codon) rRNA: ribosomal RNA  Comprises the 70 S ribosome tRNA: transfer RNA  Transfers amino acids to ribosomes for protein synthesis  Contains the anticodon (3 base sequence that is complimentary to codon on mRNA)

Genetic Code 

DNA: triplet code



mRNA: codon (complimentary to triplet code of DNA)



tRNA: anticodon (complimentary to codon)

Genetic Code 

  



Codons: code for the production of a specific amino acid 20 amino acids 3 base code Degenerative: more than 1 codon codes for an amino acid Universal: in all living organisms

Genetic Code

Translation 

Three parts:   





Initiation-start codon (AUG) Elongation-ribosome moves along mRNA Termination: stop codon reached/polypeptide released and new protein forms

rRNA=subunits that form the 70 S ribosomes (protein synthesis occurs here) tRNA=transfers amino acids to ribosomes for protein synthesis)

Genetic Transfer in Bacteria   

Genetic transfer-results in genetic variation Genetic variation-needed for evolution Three ways: 





Transformation: genes transferred from one bacterium to another as “naked” DNA Conjugation: plasmids transferred 1 bacteria to another via a pilus Transduction: DNA transferred from 1 bacteria to another by a virus

Transduction by a Bacteriophage

Transformation

Conjugation in E. coli

Conjugation continued…

Conjugation continued…