Microbiology 1 LEC 4-5

Aerobic respiration

glycolysis, kreb's cycle, and ETC using O2 as electron acceptor

Anaerobic respiration

glycolysis, kreb's cycle, and ETC using an inorganic molecule as final electron acceptor OR uses fermentation

What are glycolytic pathways

embden meyerhof pathway and entner doudoroff pathway

Embden meyerhof pathway

More common; Produces 2 pyruvate and 4 ATP

Entner-doudoroff pathway

least common; Produces 2 ethanol and 3 ATP

Alcoholic fermentation

Converts pyruvic acid into ethanol and CO2

Zymomonas mobilis

the primary alcoholic fermentation bacterial species

Homolactic fermentation

Lactic acid is the sole end product, used to ferment milk products

Which bacterial species use homolactic fermentation?

Lactobacillus, lactococcus, and most streptococci

Heterolactic fermentation

"Phosphoketolase pathway" Produces lactic acid along with ethanol, and/or acetic acid and CO2

Mixed Acid Fermentation

Produces lactic acid, acetic acid, formic acid, succinate, and ethanol.

Can also produce CO2 and H2 gas if the bacteria has formate dehydrogenase

What species of bacteria uses mixed acid fermentation?

enterobacteriaceae

Butanediol fermentation

Creates the same things as the mixed acid pathway + butanediol

What bacteria perform butanediol fermantation

glebsiella and enterobacteria

Other fermentation pathways:

(create products which they are named after)

Butyric acid

Butanol-acetone

propionic

What are the alternate pathways of ETC/anaerobic respiration

biological methanogenesis

denitrification

sulfate reduction

Biological methanogenesis

methane gas is produced and stored under anaerobic conditions

performed by methanogens

final step in the decay of organic matter

Denitrification

Removes nitrate (NO3) from the soil

Sulfate reduction

Some obligate anaerobes can reduce sulfate to hydrogen sulfide gas, only occurs under anaerobic conditions (is not an alternate, just different)

Alternate ETC pathways

can happen as an alternative to oxygen ETC in the presence of oxygen

What is the maximum number of genes for bacteria?

4000

T or F: Bacteria can contain diploid DNA

False (only haploid)

T or F: Bacterial chromosomes can be circular or linear

True

T/F most bacterial chromosomes are linear

False

Replisome (Linear) Replication

"Normal replication" Helicase, primsae, SSBP, topoisomerase, DNA polymerase and ligase

In circular DNA, there are two DNA forks for replication

This forms two new circles

Rolling circle replication

Occurs only in some bacterial viruses and plasmids

Involves synthesis of DNA in a single direction with the new strand rolling out from the circle of DBA like a paper towel

One replication fork

What are the unique features of prokaryotic transcription

simultaneous transcription and translation

read as uninterrupted series

Feedback inhibition

Non-genetic control mechanism in which end product inactivates the first enzyme in a pathway by combining with it at an allosteric site

Provides immediate course control

Constitutive enzymes

Those that are always present (glycolytic enzymes)

Operon based repression

A section in genetic code that turn on or off transcription

Induction genes

A section of the genetic sequence which upregulates transcription

Usually turned off until we want it on

sugar usage

End product repression

A part in the genetic sequence which downregulates transcription

Usually turned on unless we want it off

protein regulation

Lac operon

an inducible operon whose repressor is removed in the presence of glucose

Repressible operon

End product proteins will bind to a repressor, causing it to bind to the operator and stop transcription

heritable stability

resides in template directed, semi-conservative replication of DNA and RNA

heritable variation

achieved via mutation and/or recombination i.e. change in base sequence

Genotype

sum of genetic determinants

Phenotype

observable properties

Wild type

non-mutated form, form found in nature

Mutant

progeny expressing mutation

Nutritional mutation

"auxotroph" a mutant type unable to grow without a particular growth factor

Revertant

a mutation occurs, then another mutation occurs reverting the gene to its original state

Base substitution

the swapping of one nucleotide for another

Transition

purine for purine or pyrimidine for pyrimidine point mutation

Transversion

purine for pyrimidine or vice versa point mutation

Addition and deletion

adding or removing a single nucleotide

Missense mutation

amino acid replacement

Nonsense mutation

early placement of a stop codon

Frameshift mutation

a deletion or insertion that shifts the way a sequence is read

Regulatory mutation

mutation not occurring in regions of the DNA that actually code for the protein

Possible alterations to mutation (beneficial)

Morphology change

Genetic control mechanism

Resistance

Temperature preference

Acid preference

Osmotic regulation

Enzymatic function

Spontaneous mutation

random change in DNA arising from replication mistakes or background radiation

Induced mutations

A mutation causes by a chemical or physical mutagen (physical is often radiation)

What type of DNA transfer only happens through recombination?

transposons

Conjugation

Cell-to-cell contact

Two cells are smushed together to share plasmid DNA

What type of bacteria uses conjugation?

gram - only

F factor

ability to form a pilus, required to share DNA

R factor

resistance plasmids

Hfr Strains

high frequency recombination strains

RTF

resistance transfer factor

A plasmid with genetic info for F pilus and enzymes for neutralizing antibiotic activity

Intergeneric conjugation

seen among some enterobacteriaceae

Transformation

Transfer of free DNA, requires no special vehicle

Transduction

Transfer mediated through the action of bacterial viruses (bacteriophages)

Generalized Transduction

the bacteriophages can pick up any portion of the host's genome

Specialized Transduction

bacteriophages pick up only specific portions of the host's DNA

Transposon

Sequences of DNA that can move to different positions within the chromosome

Transposition

the moving of a transposon with DNA