2 - Brief Review of Bacteria Flashcards
1
Q
The cell membrane (plasma membrane) is responsible for a broad range of activities including _________,________,________
A
- solute transport
- electron transport
- establishment of electrochemical gradients
- ATP synthesis
- Synthesis of lipids
2
Q
Cell wall (peptidoglycan) - most bacteria are surrounded by a cell wall that protects the the cell from _________
A
bursting due to turgor pressure
3
Q
Why does turgor pressure exists?
A
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
4
Q
What are the 3 components of the Gram-positive cell wall:
A
- lipoteichoic acid
- large peptidoglycan
- plasma membrane
5
Q
What are the 3 components of the Gram-negative cell wall:
A
- outer lipid membrane
- peptidoglycan (small)
- plasma membrane
6
Q
Name the 4 steps of the Gram Stain:
A
- Application of crystal violet (purple dye)
- Application of iodine (mordant)
- Alcohol wash (decolorization)
- Application of safranin (counterstain)
7
Q
Gram + color =
A
purple
8
Q
Gram - color =
A
pink
9
Q
Why do we use the gram stain?
A
To differentiate gram positive from gram negative bacteria by using the physical properties of the cell walls (thickness/amount of peptidoglycan)
10
Q
Give the details about the steps of gram stain:
A
- 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
11
Q
Baceteria, archaea and eukarya have the same _______
A
universal ancestor
12
Q
What are the surface structures of gram + bacteria:
A
- teichoic acids
- capsule
- fimbrae and pili (some gram + bacteria)
- flagella (organelle of locomotion)
13
Q
What are the surface structure of gram - bacteria:
A
- lipopolysaccharide (consists of lipid A, core (inner/outer) and repeating Oligosaccharide (O-antigen)
- capsule
- fimbrae and pili (most gram - bacteria)
- flagella (organelle of locomotion)
14
Q
Fimbrae and pili are __________ _________ extending from the cell surface found in most gram -ve and a few gram +ve bacteria
A
protein fibrils
15
Q
many fimbrae and pili mediate __________
A
attachment to other cells or surfaces
16
Q
Adhesive pili have ________ which are proteins in the pili that allow the pili to stick to things
A
adhesins
17
Q
________ are used for bacteria to attach to each other and transmit DNA from a donor cell to a recipient cell
A
Sex Pili
18
Q
Sex pili are found in ________ bacteria but are not universal among bacteria
A
enteric (E.coli, Pseudomonas)
19
Q
In E.coli the sex pili is coded for by a conjugative transmissible plasmid ________________
A
The F-plasmid that resides in the donor strains
20
Q
Swimming bacteria have 1 or more __________
A
flagella
21
Q
Flagella is _______________
A
an organelle of locomotion that protrude from the cell surface
22
Q
Flagellum is a stiff _________ filament that rotates like a propeller
A
helical
23
Q
Name the variety of physiological and physical states that microorganisms can exist in?
A
- vegetative
- injured
- viable but not culturable
- communicating in structured communities (biofilms)
- sporulated
24
Q
______________________ can lead to Injured cells that are unable to grow on _________ media, but are able to grow on _____________ media
A
Sublethal stressors
Selective
Non-selective
25
T OR F: Injured cells are more sensitive to selective agents (i.e: antibiotics) and may have increased nutritional requirements
T
26
What do you need during the repair process?
denovo RNA and protein synthesis
27
______________ is reestablished during repair
membrane intergrity
28
is temperature critical for repair?
yes, L.monocytogenes can start repair immediately at 37C but repair is delayed for almost 1 week at 4C
29
VBNC =
viable but not culturable
30
_____________ (5) can each exist in VBNC states
Salmonella, Campylobacter, Escherichia, Shigella, Vibrio
31
___________ is a survival strategy for non-sporulating species
viable but not culturable
32
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)
33
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)
34
VBNC is most often induced by _________________
nutrient limitation
35
VBNC can be resuscitated by _________________________
temperature shifts and a gradual return of nutrients
36
Quorum sensing =
communication between bacterial cells
37
Cellular communication happens in 2 different ways:
- signal transduction
| - quorum sensing
38
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
39
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
40
T or F: Quorum sensing, in gram - bacteria (AHLs) act as signaling molecules
T
41
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
42
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
43
In signal transduction, unlike quorum sensing the trigger molecule ______________
does not diffuse into the cell
44
Two component signal transduction systems consist of a ______________ receptor and a __________________.
histidine kinase
| response regulator
45
A signal molecule binds the ___________ on the “out-side” of the membrane spanning kinase.
N-terminus
46
The protein kinase transduces the signal across the membrane via a __________________ that increases ___________ on the ____________ side.
conformational change
kinetic activity
cytoplasmic
47
This phosphorylates a response regulator protein that modulates _____________________________
gene expression, enzymatic activity, flagellar rotation or another phenotype.
48
Which signal system is used by L.monocytogenes, S.aureus & Lactic acid bacteria
Signal transduction
49
Which signal system is used by S.enterica serovar Typhymurium, E.coli & V.cholerae
Quorum sensing
50
What is a pleiotrophic effect?
it occurs when 1 gene influences 2 or more seemingly unrelated phenotypic traits
51
Biofilm:
aggregation of cells, often of multiple species, into heterogenous complex structures that are attached to a solid surface
52
Biofilms are composed by _____________ that have defined boundaries that allow fluid channels to run through the biomatrix
microcolonies
53
Biofilms, this requires some kind of cell-to-cell communication so that __________________ cells do not fill these channels
undifferentiated
54
Why are channels critical in biofilms?
Because they bring in nutrients and carry away waste
55
T or F: Biofilms are more resistant to heat, chemicals and sanitizers than planktonic cells, making them important to the food industry
T
56
___________ are differentiated cells that are very resistant to heat and cannot be easily destroyed even by chemicals
endospores
57
Bacterial genetics, the main genomic element is the ____________________
chromosome
58
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
59
Eukaryotes have ___________ chromosomes
multiple
60
Prokaryotes tend to have ______________ chromosomes, where eukaryotes have ____________ chromosomes
circular
| linear
61
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
62
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)
63
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
64
What are the 3 foodborne diseases categories?
- Infection
- Intoxication
- Toxico-infection
65
_______________ Genes that are shared by all members of a certain group (ie: bacterial species)
core genome
66
________________ Genes that are present in any member of a certain group
pangenome
67
__________________ Genes that are present in a subset of members of a certain group
accessory genome
68
Name 4 mobile genetic elements that contribute to genetic diversity in bacteria:
- bacteriophage
- plasmids
- pathogenicity islands
- transposons
69
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
70
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
71
___________ can carry genes for virulence factors or toxins required for pathogenesis by the pathogens they lysogenize
Prophages
72
______________: the process by which a prophage converts a nonpathogenic bacteria to a pathogen
lysogenic conversion
73
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
74
_________________: A bacterioprophage that can no longer form infective phage due the loss of essential genes
Defective prophage
75
_____________: Circular molecules of double-stranded DNA which are self replicating (in some exceptions they are linear).
Plasmids
76
T or F: plasmids can vary in sizes ?
T
77
T or F: plasmids can be passed from mother to daughter cells as well as between different unrelated species of bacteria
T
78
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)
79
Pathogenicity islands: they carry an __________ gene that allows them to integrate into a region of the host DNA
integrase
80
____________ are DNA elements that can hop from one place in chromosomal DNA to another
Transposons
81
What are the 2 types of of bacterial transposons:
- insertion sequence elements
| - composite transposons
82
________________: the transmission of DNA from mother to daughter cells
Vertical gene transfer
83
___________________: the movement of DNA from one bacteria organisms to another other than via vertical transmission
Horizontal gene transfer
