Bacterial Metabolism, Bacterial growth and cell division

What does an autotroph use as a carbon source?

CO2

What does heterotroph use as a carbon source?

Organic carbon

What is an obligate aerobe?

Bacteria requires oxygen

What is an obligate anaerobe?

Bacteria will die in presence of oxygen

What is an facultative anaerobe?

Bacteria can grow or without oxygen (better with oxygen)

What is the purpose of glycolysis?

Catabolize glucose to produce ATP and NADH, generates intermediates for other processes

How is ATP produced during glycolysis?

By substrate level phosphorylation (ADP + Pi = ATP)

What is the purpose of the TCA cycle?

To generate energy by breaking down molecules in cellular respiration

How much energy is generated from aerobic respiration?

Glycolysis + TCA + e-transport = 38 molecules of ATP for every molecule of glucose

How much energy is produced by glycolysis alone?

2 ATP per glucose molecule

How much ATP is produced under anaerobic conditions (fermentation)

2 ATP per glucose molecule

How do bacteria reproduce?

Asexually: 2 identical daughter cells produced

How do streptococci divide?

Division plane is linear and bacteria grows in chains

How do staphylococci divide?

Division plane is a right angle and bacteria grow in bunches

What is a septum?

A cross wall that forms when bacteria divide into two daughter cells

What is the advantage of using solid agar?

Isolation of individual, each from a single bacterium

Visualize: identify and purify different bacterial strains

Visualize contaminating bacteria and fungi

If you see blotches or unwanted colonies on the agar surface, what does this indicate?

Different colonies (by color, size, shape, texture) are also on the agar surface. Agar plates are contaminated.

What is the advantage of liquid broth media?

High-density and faster growth

Easy to monitor: growth measured by turbidity

Large Scale Production (large volumes can be grown)

What are growth stages in liquid broth?

Lag phase, log/exponential phase, stationary phase, death phase

What happens in the lag phase?

Time to adapt to environment (no significant growth)

What happens in log/exponential phase?

Significant growth

What happens in the stationary phase?

Rate of growth = rate of death

What happens in the death phase?

cells die

What are ways microbes are identified?

Phenotype, Biochemical (biotyping), Serotyping, Susceptibility to antibiotics, Lipid composition, Genotypic classification

What is the least precise way to identify a microbe?

Phenotype

What is the most precise way to identify a microbe?

Genotypic classfication

What is phenotype testing?

Colony size, shape, color (pigment) - microscope (cell shape/strain)

What is biotyping/biochemical?

Sugar fermentation, lipases, proteases,

• simple but specific

• helps distinguish members of a species

What is serotyping?

Identification based on antibodies produced by infected human, helpful if organism can’t be isolated

What is genotypic classification?

DNA

What is the binomial nomenclature?

Genus species

What is genomic sequencing?

Comparison of the DNA or RNA sequences of individual genes or whole genome

What does ribosomal RNA sequence homology determine?

Species and strain

What is PCR amplification of DNA?

technique to copy specific DNA or RNA sequences

What is DNA hybridization?

Related DNA samples will bind to each other

What is G:C ratio?

Ratio of guanine (G) to cytosine (C) residues in DNA: related organisms have a similar ratio

What is bacterial taxonomy based on?

Sequence similarity of the 16S rRNA gene.

Is ribosomal DNA translated into protein?

No, it is transcribed into RNA, not translated.

What % similarity of 16S rRNA is the minimum needed for species identification?

99%

What % similarity of 16S rRNA is ideal to claim the same species?

99.5%

What are the main steps in 16S rRNA gene sequencing?

1. Amplify (PCR) the 16S rRNA gene (~1500 bp).

2. Compare DNA sequences across organisms.

3. Determine species based on similarity (%) to other 16S rRNA sequences.