Microbial Metabolism Flashcards
In prokaryotes where is the cytoplasmic membrane located?
surrounding the cell
In eukaryotes what does the inner membrane of consist of?
mitochondrion
In respiration, a terminal electron acceptor is
used to consume donated electrons
What is oxygen commonly used as in aerobic microorganisms?
used as the acceptor
What is fermentation used by?
organisms that cannot perform respiration to consume electrons
When is fermentation used?
when oxygen is not available
What does an obligate anaerobe lack?
genes for the proteins of electron transport chain
What are fermentation products useful for?
identifying enteric bacteria
What is the central dogma of molecular biology?
DNA» Transcription (RNA)» Translation (Protein)
What is not in Prokaryotic Transcription and Translation, but is present in Eukaryotes?
mRNA is not processed and it does not contain introns
In Prokaryotes, translation occurs when?
translation of mRNA starts as it is being transcribed
In eukaryotes where is the mRNA transported so that it can be translated?
out of the nucleus so it can be transcribed in the cytoplasm
In Eukaryotes mRNA is….
In Prokaryotes mRNA is often…
Monocistronic: translation begins at the first AUG
Polycistronic: translation usually begins at the first AUG that follows a ribosome binding site
What is true about Prokaryotic gene regulation?
some genes are constitutively expressed
Most prokaryotic genes are
modulated
Repressors
bind to the DNA between the promoter and transcriptional start site, thus blocking RNA pol
Activators
interact with the promoter region to facilitate RNA pol binding
During the “off setting” what is bound?
the repressors
During the “on setting” what is bound?
The activators
What is the lac operon
a sensing pathway for lactose
What must you have for the expression of a gene that metabolizes lactose in culture media?
The presence of lactose and absence of glucose
What are the steps for turning on the LAC operon
- As Glucose levels drop cyclic AMP (cAMP) increases
- cAMP binds to catabolite activating), allowing it to bind to the promoter
- Allolactose, an isomer of lactose, binds to the lac repressor, preventing from binding to the DNA
- RNA pol binds to the DNA and begins mRNA synthesis
What are cAMP and CAP together?
they become an activator together
Permease
Protein involved in permeability, allows the glucose to get into the cell
What happens to the lac operon when Glucose is present and lactose is not present?
Transcription is not activated AND blocked;
Because there are low glucose levels there are low cAMP levels and CAP cannot bind, repressor is bound to operator blocking polymerase
What happens in the lac operon when glucose is present and lactose is present?
Transcription is not activated; low cAMP; CAP cannot bind. The inducer, allolactose, prevents repressor from binding to the operator
What happens in the lac operon when: No Glucose
No Lactose?
Transcription is activated but blocked; High cAMP; CAP/cAMP complex binds to the activator site. Repressor is bound to operator, blocking polymerase
What happens in the lac operon when; No Glucose
Lactose Present?
High cAMP; CAP/cAMP complex binds to activator binding site. Allolactose (inducer) prevents repressor from binding to the operator
What is Gene 1 in the lactose operon?
Lac Z B-galactosidase
What is Gene 2 in the lactose operon
Lac Y B-galactoside permease
What is Gene 3 in the lactose operon?
Lac A B-galactoside transacetylase
Antibiotic resistance is a
genetic event
What is MRSA
methicillin- resistant Staphylococcus aureus
Is S.aureus Gram + or Gram -
Gram +
What is now used instead of methicillin to treat Staphylococcus aureus?
Vancomycin
What does it mean to be haploid?
one chromosome: one copy of everything: Bacteria have haploid genes
What do mutations in bacterial genes alter?
alter the genotype and phenotype
What is the genotype?
DNA-level information encoded by the genome
What are phenotypes usually controlled by?
proteins by alteration of amino acid composition
What are the two types of mutations?
Induced
Spontaneous
What are Spontaneous mutations?
mutations during normal cellular processes
What are the three types of Spontaneous mutations?
Nucleotide base substitution (point mutation)
Deletion or insertion of nucleotides
Transposable elements ("jumping genes"What causes induced mutations?
Chemicals and radiation can INDUCE mutations
What enzymes are expressed during times of stress? and what do these enzymes do?
Mutases, they increase rates of mutations
What do all DNA polymerases have?
inherent mutation rates
What would not occur without mutations?
Evolution and organisms being well-equipped to adjust to changes in their environment
What three events does evolution require?
Genetic Variation (mostly random: mutations) The variations must be heritable Natural selection of those traits most suitable for environment
What are cells that are receptive to DNA?
competent
What does the process of becoming competent require?
protein synthesis
What do competent cells have the ability to do? What is this process called and what can it lead to?
permit DNA to pass through their cell walls and membranes: termed Transformation and can lead to acquisition of new genes
What can be induced artificially and play a large role in biotechnology?
Competent cells
What is transduction? What is an example of this?
Transfer of Genetic Material from one species to another: ex: Bacteriophages (bacterial viruses)
What are plasmids?
circular molecules of DNA: look like a bacterial chromosome
What do plasmids frequently contain?
Virulence factors; contribute to disease susceptibility:
Antibiotic resistance
Toxins
What are plasmids routinely used for in biotechnology?
gene cloning and recombinant protein production
Why are plasmids considered promiscuous?
they can disseminate between species of bacteria
What is conjugation
direct transfer of plasmids (or chromosomes) between bacteria
What acquire plasmids by random chance rather than conjugation?
Competent cells
What are the four steps of Conjugation?
1) Contact between donor cell (F+) and Recipient cell (F-) is mediated by a sex pilus, a tubular structure
2) The plasmid becomes mobilizes by an enzyme that cleaves the plasmid
3) One strand of the plasmid is transferred tot he recipient, presumably through the pilus
4) The copies of the plasmids are used as templates for DNA synthesis
What are Transposons?
Jumping Genes; copy themselves and then leave:
Self replicating DNA molecules
Where do transposons occur?
Virtually ALL organisms
What frequently happens when transposons jump?
They take adjacent genes with them, such that integration in another cell leads to the introduction of novel genetic information.
In General the process of protein transcription followed by translation would be faster for…
Prokaryotes
You place bacteria in a phenol red lactose broth. A change in broth color from yellow indicated that the bacteria can utilize the sugar source. In this situation you can conclude that:
Allolactose is present in the broth
