2 - Brief Review of Bacteria Flashcards
The cell membrane (plasma membrane) is responsible for a broad range of activities including _________,________,________
- solute transport
- electron transport
- establishment of electrochemical gradients
- ATP synthesis
- Synthesis of lipids
Cell wall (peptidoglycan) - most bacteria are surrounded by a cell wall that protects the the cell from _________
bursting due to turgor pressure
Why does turgor pressure exists?
Because bacteria live in environments that are more dilute tan the cytoplasm. This causes a net influx of water. This results in pressure (turgor) being directed out against the cell wall
What are the 3 components of the Gram-positive cell wall:
- lipoteichoic acid
- large peptidoglycan
- plasma membrane
What are the 3 components of the Gram-negative cell wall:
- outer lipid membrane
- peptidoglycan (small)
- plasma membrane
Name the 4 steps of the Gram Stain:
- Application of crystal violet (purple dye)
- Application of iodine (mordant)
- Alcohol wash (decolorization)
- Application of safranin (counterstain)
Gram + color =
purple
Gram - color =
pink
Why do we use the gram stain?
To differentiate gram positive from gram negative bacteria by using the physical properties of the cell walls (thickness/amount of peptidoglycan)
Give the details about the steps of gram stain:
- Cells are dyed with crystal violet dye, iodide is added, this binds crystal violet and traps it in the peptidoglycan (called a mordant)
- Cells are destained using ethanol or acetone
- Gram-positive cells retain the dye and remain violet, gram-negative cells lose their colour
- Counterstaining is then preformed with Safranin or Carbol Fushin which stains Gram-Negative cells pink or red, allowing them to show up under light microscopy
Baceteria, archaea and eukarya have the same _______
universal ancestor
What are the surface structures of gram + bacteria:
- teichoic acids
- capsule
- fimbrae and pili (some gram + bacteria)
- flagella (organelle of locomotion)
What are the surface structure of gram - bacteria:
- lipopolysaccharide (consists of lipid A, core (inner/outer) and repeating Oligosaccharide (O-antigen)
- capsule
- fimbrae and pili (most gram - bacteria)
- flagella (organelle of locomotion)
Fimbrae and pili are __________ _________ extending from the cell surface found in most gram -ve and a few gram +ve bacteria
protein fibrils
many fimbrae and pili mediate __________
attachment to other cells or surfaces
Adhesive pili have ________ which are proteins in the pili that allow the pili to stick to things
adhesins
________ are used for bacteria to attach to each other and transmit DNA from a donor cell to a recipient cell
Sex Pili
Sex pili are found in ________ bacteria but are not universal among bacteria
enteric (E.coli, Pseudomonas)
In E.coli the sex pili is coded for by a conjugative transmissible plasmid ________________
The F-plasmid that resides in the donor strains
Swimming bacteria have 1 or more __________
flagella
Flagella is _______________
an organelle of locomotion that protrude from the cell surface
Flagellum is a stiff _________ filament that rotates like a propeller
helical
Name the variety of physiological and physical states that microorganisms can exist in?
- vegetative
- injured
- viable but not culturable
- communicating in structured communities (biofilms)
- sporulated
______________________ can lead to Injured cells that are unable to grow on _________ media, but are able to grow on _____________ media
Sublethal stressors
Selective
Non-selective
T OR F: Injured cells are more sensitive to selective agents (i.e: antibiotics) and may have increased nutritional requirements
T
What do you need during the repair process?
denovo RNA and protein synthesis
______________ is reestablished during repair
membrane intergrity
is temperature critical for repair?
yes, L.monocytogenes can start repair immediately at 37C but repair is delayed for almost 1 week at 4C
VBNC =
viable but not culturable
_____________ (5) can each exist in VBNC states
Salmonella, Campylobacter, Escherichia, Shigella, Vibrio
___________ is a survival strategy for non-sporulating species
viable but not culturable
How can you demonstrate viability (cytological methods)?
verify the structural integrity of the bacterial cytoplasmic membrane by fluorescent nucleic strains (red), if they permeate the cell it indicates the cell is dead, green counter stain is used to stain the cell wall (green), bacterias with intact cell membranes stain green (viable)
How can you demonstrate viability (substrate responsive metabolism)?
cells can be incubated with a nutrient (yeast extract) and an antibiotic that inhibits cell division (ciprofoxacin), live cells elongate, but do not divide, this can be quantified microscopically (method specific for listeria)
VBNC is most often induced by _________________
nutrient limitation
VBNC can be resuscitated by _________________________
temperature shifts and a gradual return of nutrients
Quorum sensing =
communication between bacterial cells
Cellular communication happens in 2 different ways:
- signal transduction
- quorum sensing
Signal transduction:
2 component regulatory systems where 1 protein spans the membrane, picks up a signal and then reacts based on a response regulator protein
Quorum sensing:
systems are built on autoinducers which diffuse through the cellular membrane to initiate a specific response when a certain population density has been reached
T or F: Quorum sensing, in gram - bacteria (AHLs) act as signaling molecules
T
T or F: Probiotic bacteria have been shown to prevent infection by pathogenic bacteria but the mechanism of how is still not entirely understood
T
It is thought that _____________________ prevents E. coli O157:H7 infection by producing small biologically active molecules that interfere with the quorum sensing systems of E. coli O157:H7, this limits the ability of the pathogen to adhere to tissues and cause lesions
Lactobacillus acidophilus
In signal transduction, unlike quorum sensing the trigger molecule ______________
does not diffuse into the cell
Two component signal transduction systems consist of a ______________ receptor and a __________________.
histidine kinase
response regulator
A signal molecule binds the ___________ on the “out-side” of the membrane spanning kinase.
N-terminus
The protein kinase transduces the signal across the membrane via a __________________ that increases ___________ on the ____________ side.
conformational change
kinetic activity
cytoplasmic
This phosphorylates a response regulator protein that modulates _____________________________
gene expression, enzymatic activity, flagellar rotation or another phenotype.
Which signal system is used by L.monocytogenes, S.aureus & Lactic acid bacteria
Signal transduction
Which signal system is used by S.enterica serovar Typhymurium, E.coli & V.cholerae
Quorum sensing
What is a pleiotrophic effect?
it occurs when 1 gene influences 2 or more seemingly unrelated phenotypic traits
Biofilm:
aggregation of cells, often of multiple species, into heterogenous complex structures that are attached to a solid surface
Biofilms are composed by _____________ that have defined boundaries that allow fluid channels to run through the biomatrix
microcolonies
Biofilms, this requires some kind of cell-to-cell communication so that __________________ cells do not fill these channels
undifferentiated
Why are channels critical in biofilms?
Because they bring in nutrients and carry away waste
T or F: Biofilms are more resistant to heat, chemicals and sanitizers than planktonic cells, making them important to the food industry
T
___________ are differentiated cells that are very resistant to heat and cannot be easily destroyed even by chemicals
endospores
Bacterial genetics, the main genomic element is the ____________________
chromosome
T or F: Most typical prokaryotes have a single chromosome (with some exceptions i.e. Vibrios have a two) that contain most of the genes of that cell
T
Eukaryotes have ___________ chromosomes
multiple
Prokaryotes tend to have ______________ chromosomes, where eukaryotes have ____________ chromosomes
circular
linear
Toxicoinfections:
illness occurs from the ingestion of a large number of viable cells of some pathogenic bacteria through the consumption of contaminated food or water, the bacterial cells either sporulate, colonize or die, and release the toxins
Infection:
Illness occurs after the consumption of viable bacterial cells or viruses, the viable cells even in low numbers are able to multiply in the digestive tract and cause illness (with bottom or top end sysmptoms)
Intoxication:
This occurs after the ingestion of a bacterial or mould toxin, due to the growth of the bacteria or mould in the food, the toxin must be present in its active form, once the toxin has been produced the viability of the microorganism is no longer relevant , toxins are often better able to withstand processing better than the organism
What are the 3 foodborne diseases categories?
- Infection
- Intoxication
- Toxico-infection
_______________ Genes that are shared by all members of a certain group (ie: bacterial species)
core genome
________________ Genes that are present in any member of a certain group
pangenome
__________________ Genes that are present in a subset of members of a certain group
accessory genome
Name 4 mobile genetic elements that contribute to genetic diversity in bacteria:
- bacteriophage
- plasmids
- pathogenicity islands
- transposons
Explain the steps in lytic bacteriophage:
1) Virus particle attaches and injects its DNA inside the bacterial cell
2) Viral DNA replicates
3) Coat proteins are synthesized, virus particles are assembled
4) Bacterial cell lyses, this releases new infectious virus particles
Explain the steps in lysogenic bacteriophage:
1) Virus particle attaches and injects its DNA inside the bacterial cell
2) Viral DNA is integrated into the host DNA
3) Cell division
4) Normal cell growth
___________ can carry genes for virulence factors or toxins required for pathogenesis by the pathogens they lysogenize
Prophages
______________: the process by which a prophage converts a nonpathogenic bacteria to a pathogen
lysogenic conversion
T or F: Vibrio cholerae is not pathogenic until infected with a phage (CTX), the phage integrates at a specific site in the chromosome and carries the gene for the Cholera toxin (the only factor required for illness)
T
_________________: A bacterioprophage that can no longer form infective phage due the loss of essential genes
Defective prophage
_____________: Circular molecules of double-stranded DNA which are self replicating (in some exceptions they are linear).
Plasmids
T or F: plasmids can vary in sizes ?
T
T or F: plasmids can be passed from mother to daughter cells as well as between different unrelated species of bacteria
T
T or F: plasmids carry essential genes
F, they don’t carry essential genes, they carry genes which encode for products which can benefit the bacteria under certain circumstances (ie: AMR genes)
Pathogenicity islands: they carry an __________ gene that allows them to integrate into a region of the host DNA
integrase
____________ are DNA elements that can hop from one place in chromosomal DNA to another
Transposons
What are the 2 types of of bacterial transposons:
- insertion sequence elements
- composite transposons
________________: the transmission of DNA from mother to daughter cells
Vertical gene transfer
___________________: the movement of DNA from one bacteria organisms to another other than via vertical transmission
Horizontal gene transfer
