MICR 351 Bacterial Growth Notes
Essential nutrients Macronutrients Micronutrients Growth factors - -specific nutrients not required by all cells (NAD, amino acids, viramin K)
Defined minimal mediun - -contains only the compounds needed for an organism to
MICR 351 Cell Structure and Function II Notes
cell wall - -confers shape and rigidity to the cell
-helps the cell to withstand turgor pressure
-consists of a single interlinked molecule
mycoplasma - -no cell wall
gram-positive - -bacterial ce
MICR 351 Control of Bacterial Growth Notes
Water activity - -A measure of how much water is available for use
Osmolarity - A measure of the number of solute molecules in a solution and is inversely related
to water activity
Aquaporins - Membrane-channel p
MICR 351 Genomes and Plasmids Notes
genome - -all the genetic information that defines and organism
-usually consist of one or more DNA chromosomes
-all chromosomes are DNA (exception: RNA viruses)
nitrogenous base, deoxyribose sugar, phosphate - what are
MICR 351 Exam 2 Quiz
b - why can't bacteria grow in solutions with very high concentrations of sugar?
a) bacteria cannot digest pure sugar
b) sugar raises the solution's osmolarity
c) sugar lowers the solution's osmolarity
d) sugar raises the solution's p
MICR 351 Chapter 1 Microbial Life Origin and Discovery Notes
microbe - -a living organism that requires a microscope to be seen
-often consist of a single cell
-contains in its genome the capacity to reproduce its own kind
virus - consists of a noncellula
MICR 351 Microscopy Notes
10-100 um (micrometers) - what is the range of size of eukaryotic microbes (protozoa, algae,
0.4-10 um (micrometers) - what is the range of size of prokaryotes (bacteria, archaea)?
human eye (1 mm-150 um), light microscop
MICR 351 Bacterial Growth and Control Notes
Forespore, endospore - Starvation initiates an elaborate 8-hour genetic program that involves: an
Cyanobacterial heterocysts - -differentiation of cells into heterocysts
-allows it to fix nitrogen
Two-component and phosphorelay systems
Two-component systems involve a sensor histidine
kinase protein and a response regulator protein.
The sensor histidine kinase phosphorylates itself
at a histidine in response to an environmental signal.
Regulation of gene expression
Reasons for a cell to regulate gene expression:
To avoid wasting energy on RNA and proteins that are
To turn off genes whose products may interfere with other
processes in the cell at that time.
To regulate the
The trp operon of E. coli
A negatively regulated biosynthetic operon
Regulation of a biosynthetic operon is the opposite
of a catabolic (degradative) operon such as the lac
Enzymes of a biosynthetic operon should not be
made in the presence of t
Regulation of transposition
Transposons negatively regulate their acivity to ensure that they transpose infrequently.
In Tn3, TnpR is a repressor of the transposase.
In Tn10, translation of the transposase is inhibited by an antisense RNA.
Lysis or Lysogeny?
The decision lies in CII abundance.
Lysis or Lysogeny?
The decision lies in CII abundance.
Induction of from the lysogenic to the lytic
phase is triggered by DNA damage in the host.
The phage is thought to jump ship from
Suppressors in phage
Test to distinguish suppressor mutations
Crick et al. used T4 to uncover the nature of
the genetic code.
First, they isolated frameshift mutations in a phage
Second, they isolated suppressor mutations in the
Partitioning of plasmids
As with the chromosome, the system that partitions plasmids to each
daughter cell is called the par system.
Plasmids, like the chromosome, replicate at the center of the cell.
Partitioning systems for low copy plasmids fall int
Has both lytic and lysogenic lifestyles
About 1% of infected host cells will become a lysogen, which refers to a bacterium in which a phage
genome replicates as part of the bacterial chromosome or as a plasmid.
The phage genome in a lysogen is r
Methyl-directed mismatch repair (MDMR)
General repair mechanism that recognizes
minor distortion of the DNA helix.
Responsible for repair of:
incorporation of base analogs
alkylation of bases
Complementation tests with phage
Recombination tests with phage
Infect a nonpermissive host with two mutant
phage that have lost the ability to infect this bacterium
Use a high multiplicity of infection (MOI; 5 phage
per 1 bacterial cell is considered h
Uptake of naked, free DNA by cell
Bacteria capable of being transformed are said to be competent
Some bacteria are naturally competent (Bacillus subtilis,
Streptococcus pneumoniae, Haemophilus influenzae, Neisseria
gonorrhoeae, and some
Mechanism of Conjugation
Transfer of DNA from one cell to another
Donor cell transfers DNA to a recipient cell
Recipient that has received DNA is called a transconjugant
Plasmids that encode genes for their transfer are called
Mutations can be complemented to restore
the WT phenotype by supplying a WT copy
of the gene to the mutant.
Complementation by introduction of a library of
WT DNA on a replicating plasmid to the mutant
can be used to identify the site of
The genetic code
The initiation and termination codons determine an open reading frame (ORF).
For any area of DNA sequence, there are 2 possible RNAs that could be made, each of
which has 3 possible reading frames, for a total of 6.
Isolation of mutator strains to identify genes for DNA repair
Mutator strains have a mutation in a gene that is involved in DNA repair, and as a result have a higher
rate of mutation than the wild type.
To identify mutator strains, a Lac- strain was use
RNA degradation and decay
RNA degradation can be divided into two different stages: Functional decay occurs when an endonuclase
cleaves the RNA into smaller pieces. The RNA is non-functional at this point, but the same mass of RNA
still exists. Mass deca
Post-translational regulation - localization
Inner membrane, outer membrane, periplasmic,
and secreted proteins must pass through a
membrane to get to their final location.
A signal sequence, which is cleaved off in the
case of proteins that pass throug
Not all DNA is transcribed into RNA. Instead, cis-acting
elements on the DNA called promoters direct RNA
polymerase to regions of DNA to be transcribed.
The strength of a promoter - its ability to attract RNA
polymerase - determin
Base-pair substitutions: transitions and transversions
Mispairing during replication can result in single base pair
Mispairing is promoted by alternate forms of bases that pair
differently than the normal form of the base.
For example, all f
tmRNA and stalled ribosomes
If a ribosome reaches the end of an mRNA before it reaches a stop codon,
release factors will not load without the help of a tmRNA.
tmRNA is both a tRNA and an mRNA. It is charged with alanine and
can enter the A site if a ri