Week 5: Bacteria Flashcards
1
Q
How are prokaryotes classified?
A
Based on shape, staining patterns, and genetic sequences
2
Q
How are bacteria traditionally grouped?
A
Gram-positive
Gram-negative
Atypical
3
Q
What do modern classifications also include?
A
Proteobacteria
Gram-positive bacteria with varying guanine-cytosine content
4
Q
How do we classify Bacteria?
A
Scientific name
Shape
Need for oxygen
Genetic makeup
How we stain them
5
Q
Linnaeus developed what?
A
Binomial nomenclature
6
Q
What is Binomial nomenclature?
A
Two-word naming system (Genus and species)
7
Q
Where are most naming sources from?
A
Derived from Latin, Greek, or English
8
Q
What are Cocci bacteria?
A
Small, round, oval, or spherical bacteria.
From the Greek word “kokkos” which translates to berry or seed.
9
Q
What are Bacilli?
A
Little rod shaped bacteria ranging from short & stubby, to long and filamentous.
Derived from “bacillus” which means little rod.
10
Q
What are some other bacteria shapes?
A
Vibrio (tear drop)
Spirilla
Spirochetes
11
Q
What does it mean when a bacteria is Pleomorphic?
A
It can change its shape
12
Q
What are Obligate Aerobes?
A
Require oxygen for growth; use oxygen for cellular respiration (e.g., Mycobacterium tuberculosis).
13
Q
What are Obligate Anaerobes?
A
Cannot tolerate oxygen; growth occurs only
in oxygen-free environments (e.g., Clostridium botulinum).
14
Q
What are Facultative Anaerobes?
A
Can grow with or without oxygen; prefer oxygen for energy production but can switch to anaerobic metabolism (e.g., Escherichia coli).
15
Q
What are Aerotolerant Anaerobes?
A
Do not use oxygen but can tolerate its presence; rely on fermentation (e.g., Streptococcus pyogenes).
16
Q
What are Microaerophiles?
A
Require low levels of oxygen (lower than atmospheric levels) for growth (e.g., Helicobacter pylori).
17
Q
What is G+C content?
A
Measures the proportion of guanine (G) and cytosine (C) in the bacterial DNA.
18
Q
What does measuring G+C content help with?
A
High G+C vs. Low G+C content helps distinguish between different bacterial groups (e.g., Actinobacteria vs. Bacilli).
19
Q
What is 16s rRNA Gene Sequencing?
A
Analyzes the sequence of the 16S ribosomal RNA gene, a highly conserved region in bacterial genomes.
20
Q
How is 16s rRNA Gene Sequencing used for identification?
A
Used for identifying and classifying bacteria at the genus and species level.
21
Q
What is Whole Genome Sequencing (WGS)?
A
Involves sequencing the entire DNA of a bacterium.
22
Q
What does Whole Genome Sequencing provide?
A
Provides comprehensive information for precise classification, including strain-level differences.
23
Q
What did Hans Christian Gram develop in 1884?
A
The Gram Test
24
Q
What are the 3 results a Gram test can provide?
A
Gram-positive
Gram-negative
Atypical
25
Visibly, what is noticeable about a Gram-POSITIVE bacteria?
Thick peptidoglycan layer that retains crystal violent stain, remains purple
26
Visibly, what is noticeable about a Gram-NEGATIVE bacteria?
Thin peptidoglycan layer that does not retain crystal violet stain, appears
pink/red after safranin
27
How are Gram-POSITIVE bacteria classified?
Classified by guanine and cytosine nucleotide
content into low G+C and high G+C
28
How are Gram-NEGATIVE bacteria classified?
Classified into groups like
Proteobacteria, CFB, and spirochetes
29
What are some examples of Gram-POSITIVE pathogens?
- Low G+C: Bacillus anthracis (anthrax), Clostridium
tetani (tetanus), Listeria monocytogenes (listeriosis)
- High G+C: Corynebacterium diphtheriae (diphtheria), Mycobacterium tuberculosis (tuberculosis)
30
What are some examples of Gram-NEGATIVE pathogens?
- Proteobacteria: E. coli, Bordetella pertussis (whooping cough)
- CFB: Bacteroides (part of normal gut microbiota)
- Spirochetes: Treponema pallidum (syphilis)
31
What is the Gram Stain procedure?
1. Crystal violet is applied to a heat-fixed smear which turns all cells purple.
2. Gram's iodine is then added to trap the crystal violet in cells with thick peptidoglycan layers.
3. A decolourizing agent (ethanol) is used; cells with thick peptidoglycan layers retain the purple colour, thin layers lose the dye.
4. A secondary stain (safranin) is applied to stain the decolourized cells pink, while the purple-stained cells remain purple.
32
What are some other forms of Staining?
Acid-Fast stain
Capsule stain
Endospore stain
Flagella stain
33
What is Acid-Fast staining?
Differentiates bacteria with waxy cell walls (e.g., Mycobacterium species) using carbol fuchsin and methylene blue.
34
What is Capsule staining?
Negative staining technique that highlights protective capsules around bacteria by staining the background
35
What is Endospore staining?
Uses malachite green and safranin to identify tough, dormant endospores within bacterial cells.
36
What is Flagella staining?
Thickens and stains bacterial flagella to make
them visible under a light microscope, aiding in classification.
37
T or F: An estimated 20% of animal bites or scratches cause infection in humans
True
38
What are some examples of Companion Animal-Borne Zoonoses?
Cat-scratch Disease
Pasteurella Infections
Campylobacter Infections
39
What is Cat-Scratch Disease?
Transmitted through cat scratches or bites.
Causes skin lesions, fever, and swollen lymph nodes, with risks of severe complications in immunocompromised individuals.
40
What are Pasteurella Infections?
Often result from dog or cat bites, leading to rapid infection at the bite site, with potential complications like cellulitis and abscess formation.
41
What are Campylobacter Infections?
Campylobacteriosis can be transmitted from animals to humans through the fecal-oral route.
The risk of infection is significantly increased by feeding pets raw food diets, which can harbour the bacteria.
42
What are some common Farm Animal-Borne Bacterial Zoonoses?
Salmonellosis (Salmonella spp.)
Bovine Tuberculosis
Q Fever
43
What is Salmonellosis (salmonella spp.)?
A food-borne bacterial infection transmitted through consuming contaminated eggs, poultry, or other foods.
Can cause severe diarrhea, sometimes with blood, and
poses a particular risk to young children and the elderly, potentially leading to life-threatening complications or permanent kidney damage.
44
What is Bovine Tuberculosis?
Caused by M. bovis, primarily affects cattle but can be transmitted to humans through direct contact with infected animals or the consumption of unpasteurized dairy products.
45
What is Q Fever?
Spread by inhalation of particles from infected animals or through unpasteurized dairy products, causing flu-
like symptoms that can persist for months.
46
What are some examples of Vector-Borne Bacterial Zoonoses?
Lyme Disease
Tularemia
47
What is Lyme Disease?
Transmitted by ticks, causing rash, joint pain, and potential neurological issues.
Common in areas where
humans and ticks coexist.
48
What is Tularemia?
Spread through tick bites, handling infected animals, or inhaling contaminated dust, leading to symptoms that vary from skin ulcers to pneumonia.
49
What are two types of Gram-Negative Bacteria?
Proteobacteria
Nonproteobacteria
50
What are Proteobacteria?
Gram-negative bacteria that can be found in the human
microbiome and other pathogenic species
51
What are the 5 distinct classes of Proteobacteria?
1. Alphaproteobacteria
2. Betaproteobacteria
3. Gammaproteobacteria
4. Deltaproteobacteria
5. Epsilonproteobacteria
52
What are Alphaproteobacteria known as?
The Oligotrophs
53
Where do Alphaproteobacteria thrive?
In low-nutrient environments such as deep oceanic sediments, glacial ice, and soil
54
What are the 2 Key Genera of Alphaproteobacteria?
Rickettsia
Chlamydia
55
Rickettsia rickettsia causes which disease that is transmitted by tick bites?
Rocky Mountain spotted fever
56
Chlamydia trachomatis is a human pathogen responsible for what?
Trachoma and lymphogranuloma venereum (LGV).
57
What are Betaproteobacteria known as?
The Eutrophs
58
Where do Betaproteobacteria thrive?
In areas with high levels of organic nutrients and often inhabit areas between aerobic and anaerobic zones
59
What are some notable Betaproteobacteria pathogens?
Neisseria gonorrhoeae
Neisseria meningitidis
Bordetella pertussis
60
What does Bordetella pertussis cause?
Whooping cough.
It produces toxins that damage respiratory cells.
61
What are Gammaproteobacteria known as?
The Diverse Group
62
T or F: Gammaproteobacteria DOES NOT include many human pathogens
False
63
What are some examples of Gammaproteobacteria?
Pseudomonas aeruginosa
E. coli
Vibrio cholerae
64
What does E. coli cause?
Severe GI diseases
65
What does Vibrio cholerae cause?
Cholera
Leads to severe dehydration through profuse watery diarrhea
66
What are Deltaproteobacteria known as?
Sulfate Reducers and Predators
67
What are some examples of Deltaproteobacteria?
Desulfovibrio orale
Bdellovibrio species
Myxobacteria
68
What does Desulfovibrio orale cause?
Periodontal disease
69
What do the Bdellovibrio species do?
They are parasites of other gram-negative bacteria, invading and consuming host cells.
70
What do Myxobacteria do?
Form multicellular fruiting bodies and myxospores, showcasing complex social behavior.
71
What are Epsilonproteobacteria known as?
The Smallest class
72
What is special about the Epsilonproteobacteria?
They are microaerophilic, meaning they require low oxygen levels
73
What are some examples of Epsilonproteobacteria?
Campylobacter jejuni
Helicobacter pylori
74
What is Campylobacter jejuni?
It is a common cause of food poisoning through contaminated poultry, leading to severe enteritis.
75
What is H. pylori?
It survives in the acidic environment of the stomach and causes chronic gastritis, peptic ulcers, and is linked to stomach cancer.
76
What are Gram-Negative Nonproteobacteria?
Nonproteobacteria are gram-negative bacteria that do not belong to the phylum Proteobacteria.
77
What are the 3 primary classes of Nonproteobacteria?
1. Spirochetes
2. CFB (Cytophaga, Fusobacterium, Bacteroides)
3. Planctomycetes
78
What are Spirochetes?
Long spiral-shaped bodies
Includes pathogens like Treponema pallidum (causes syphilis) and Borrelia burgdorferi (Lyme disease)
79
What is the CFB Group?
Anaerobic species which includes Cytophaga, Fusobacterium, and
Bacteroides—key players in human health and disease
80
T or F: Bacteroides make up 30% of the gut biome.
True
81
What are Planctomycetes?
Unique aquatic bacteria with unusual reproductive and metabolic
features.
82
What are Phototrophic Bacteria?
- A diverse group that harness sunlight for
energy through photosynthesis.
- Generally not harmful to
humans, except (cyanobacterial blooms “blue-green algae” produce toxins which have been implicated in tumors of the liver and neurological disease).
83
What are High G+C Gram-Positive bacteria (Actinobacteria)
characteristics?
- Large and diverse phyla.
- Bacteria vary in shape and size.
- G+C content greater than 50%.
- Found in diverse environments (soil, water).
- Cell walls contain peptidoglycans.
84
What is the G+C content found in Actinobacteria?
50% up to 70%
85
What are some examples of Actinobacteria?
Mycobacterium
Corynebacterium
Bifidobacterium
Streptomyces
86
What is an example of Mycobacterium?
Includes M. tuberculosis, which causes tuberculosis, and M. leprae, which causes leprosy.
87
What is a unique feature of Mycobacterium?
Waxy mycolic acid coat that resists Gram staining (instead, acid-fast staining
must be used)
88
What is an example of Corynebacterium?
C. diphtheriae, which causes diphtheria.
89
What type of morphology are Corynebacterium?
V-shaped pairs (palisades)
90
Where are Bifidobacterium found?
Commonly found in the human gut, vagina, and mouth
91
What are Bifidobacterium used for?
Used as probiotics and in yogurt production.
92
What are Streptomyces?
A filamentous, spore-forming bacteria found in soil and used for antibiotic production (streptomycin).
93
What are Low G+C Gram-Positive bacteria characteristics?
- G+C content of less than 50%.
- Includes many pathogenic genera.
- Bacilli and cocci morphologies.
- Important for human health and industry.
94
What are Clostridium bacteria?
Rod-shaped, spore-forming anaerobes
95
What are some examples of Clostridium?
C. perfringes
C. tentani (tetanus)
C. botulinum
C. difficile
96
What are Streptococcus bacteria?
Spherical cocci, forming chains or pairs.
97
What are some examples of Streptococcus?
S. pyrogens (strep throat)
S. pneumoniae (pneumonia)
S. agalactiae
98
What are Bacillus bacteria?
Rod-shaped, form chains, spore-forming
99
What are some examples of Bacillus?
B. anthracis
B. cereus
100
What are Staphylococcus bacteria?
Spherical cocci, clusters resembling groups
101
What are some examples of Staphylococcus?
S. aureus
S. epidermidis
102
What are Mycoplasmas (shape-shifting bacteria)?
They are pleomorphic, wall-less bacteria
103
What are characteristics of Mycoplasmas (shape-shifting bacteria)?
- Lack a cell wall so are not stained by Gram-stain.
- Extremely small (some as small as 0.2um).
- Pleomorphic.
- Over 100 species identified.
104
What are notable species of Mycoplasmas (shape-shifting bacteria)?
M. pneumoniae (causes walking pneumonia)
105
What are the 10 steps of Laboratory Workflow?
1. Specimen receipt and logging
2. Direct examination
3. Specimen inoculation
4. Incubation
5. Initial plate examination
6. Subculture and Isolation
7. Bacterial identification
8. Antibiotic susceptibility testing
9. Results reporting
10. Storage and disposal
106
Laboratory errors are typically divided into these 3 phases:
1. Pre-analytical
2. Analytical
3. Post-analytical
