1
Q
Bacterial diversity
A
adapted to various environmental niches, aside from the most extreme ones (like temperatures over 100° C)
- About 16000 species of bacteria given a scientific name
- Estimated to have 700000 – 1.4 million species of bacteria in total
2
Q
How are new species identified
A
Detect 16S rRNA genes in environmental samples to accelerate identification of new species
3
Q
Proteobacteria
A
- Gram negative
- Very diverse: variety of free-living and symbiotic microbes
- Photoautotrophs, chemoheterotrophs, etc.
- Escherichia coli, Vibrio cholerae, etc.
- Ancestors of eukaryotic mitochondria via endosymbiosis
4
Q
Cyanobacteria
A
- Gram negative
- Only bacterial photoautotroph which does oxygenic photosynthesis
- Ancestors of eukaryotic chloroplasts via endosymbiosis
5
Q
Gram-positive bacteria
A
- Gram positive
- Very diverse: variety of free-living and symbiotic microbes
- Mainly chemoheterotroph
- Staphylococcus aureus, Bacillus anthracis, Bacillus subtilis, Lactobacillus bulgaricus, etc.
- Mycobacterium tuberculosis (although M. tuberculosis does not have a conventional Gram positive cell wall)
6
Q
Chlamydias
A
- ‘Gram negative’
- Obligate parasites, survival inside host cells
- No peptidoglycan cell wall
7
Q
Spirochetes
A
- Gram negative
- Some are free-living, some symbiotic
- Borrelia burgdorferi, causative agent of Lyme disease, etc.
8
Q
Lyme disease
A
- Caused by B. burgdorferi
- Bacteria carried by ticks
- debilitating arthritis, heart diseases, etc.
9
Q
Symbiosis
A
two different species living together
in close relationship
10
Q
Symbiont
A
(usually the smaller species) lives with
their host
11
Q
Types of symbiotic relationship
A
- Mutualism: both host and symbiont gain benefit
- Commensalism: one of the species gain benefit, the other is not harmed
- Parasitism: one of the species harm the other for their benefit, causing disease in many cases
12
Q
Many bacteria are human
A
symbionts, co- existing on our ‘surface’
* Skin, mouth, respiratory tract, intestine, vagina, etc
13
Q
Humans co-exist with numerous
A
microbes
* It’s estimated that there are at least equal number of symbiote microbes living on our body as compared to the number of human cells
* Some estimate up to 10 times more microbial cells
14
Q
Disease
A
disturbance in the normal functioning of an organism
15
Q
Infectious disease:
A
any disease caused by a microorganism
16
Q
Bacteria, eukaryotic protists, fungi and viruses are all known to have species who
A
cause diseases in humans
17
Q
Members of Archaea have not been
A
conclusively associated with any
specific disease
18
Q
Mycobacterium tuberculosis
A
Causative agent of tuberculosis
19
Q
Halobacterium sp.
A
- Extremophile Archaea
- requires extreme amounts of salt in environment for survival
20
Q
Pathogen
A
is a microorganism that causes a specific disease
21
Q
Pathogenesis
A
is the process which a pathogen causes
the disease
22
Q
Requirements of pathogenesis
A
- Entry into host
- Attach and invade host cells/tissues
- Evade host defenses
- Obtain nutrients from the host and reproduce
- Exit from the original point of infection and spread
23
Q
How does Biofilm helps pathogenesis
A
- Secretion of capsule/slime layer forms structures to support bacterial communities to co-exist
- Helps with attachment and evasion of host defense
24
Q
What are biofilms
A
collection of microorganisms that stick together and to a surface, forming a slimy layer
25
Pseudomonas aeruginosa
* Pathogenic, Gram negative proteobacteria
26
Bacteria causes various diseases, and many are named after the disease
* Bacillus anthracis causes anthrax
* Mycobacterium tuberculosis causes tuberculosis
* Vibrio cholerae causes cholera
27
Bubonic plague (Black Death)
* Caused by Yersinia pestis, Gram negative, non-motile coccobacillus
* Transmission via fleas
* Ravaged human population worldwide in 1340s, and killed about 1/3 of European population
* A couple thousand cases are still reported today every year
28
Obligate pathogens
Bacteria which will cause the disease in the pathogen (at least by a high chance)
29
Opportunistic pathogens
* Bacteria co-exists as part of the host's normal microbiome
* Only begins to cause disease after a trigger, such as decrease in host's immune system
30
Mannheimia haemolytica
* Gram negative bacillus
* Normally lives in the upper respiratory tract of healthy farm animals such as cows
31
Bovine pneumonic pasteurellosis (BPP)
- Acute pneumonia accompanied by fever, nasal discharge, lack of movement and loss of appetite
* BPP rarely occurs when animals are kept healthy and without stress
32
BPP happens when animals are put under stress, such as long distant transportation commonly called
The shipping fever
33
M. haemolytica is an
opportunistic pathogen which causes BPP when animals are stressed
34
How is M. haemolytica kept under control in healthy animals
* Host's immune mechanisms keep bacterial population low in the upper respiratory tract
* Some M. haemolytica may travel down the lung but are quickly cleared/purged
35
How does stress compromise the animal's immune system
* Increased bacterial population in the nasopharynx
* More M. haemolytica travels down the lung, colonizing the region
36
Escherichia coli
* Gram negative bacillus
* Normal resident of animal intestines, many are non- pathogenic
37
E. coli O157:H7
* E. coli serotype with O-antigen 157 and H-antigen 7
* One of the most frequently isolated E.coli serotype in food poisoning
Normal resident of bovine intestine
* Transmitted to humans via contaminated food
Severe, acute hemorrhagic diarrhea and abdominal cramps
38
Pathogenic bacteria may produce two categories of toxins
Exotoxin: toxins produced by the bacteria which are excreted to 'attack' the host
* E. coli O157:H7 produces Shiga toxins
Endotoxin: outermost layer of Gram negative outer membrane which has many sugars attached to it
* Gets released when the cell is killed and elicits a strong immune response of host
* Also called Lipopolysaccharide (LPS)
* Sugars at the further end of LPS is called the O- antigen (E. coli O-157:H7 has 'O-antigen type 157')
39
Bacillus antraxis
* Gram positive streptobacillus
* Causative agent of anthrax
* Spore forming, as with many other members of the genus Bacillus
* The only obligate pathogen in the genus
40
Anthrax
Skin infection via contact, lung infection via inhalation, may become fatal if untreated
41
B. antraxis spores have been used for
bioterrorism
For example, Late 2001 in USA
* Physically mailing B. antraxis spores
* 5 victims killed, more hospitalized
42
Traditional techniques suppress microbial growth to preserve food
Storage in antimicrobial chemicals
* Sugars and salts make water moves outwards from the cell (osmotic pressure)
* Vinegars, alcohol, oil are antimicrobials too
* Other steps while preparing these foods also contribute to suppressing microbes (boiling while making jams, etc.)
Fermentation
* Fermentation may produce antimicrobial chemicals such as acids and alcohols
Drying
* Removal of water prevents microbial growth
* Especially when sun-dried, as UV-radiation also suppresses microbes
Smoking
* Smoke is an antimicrobial
* Usually combined with drying/salting
Canning
* Pack food in a well-sealed container
* Remove microorganisms in the can by
boiling etc
Cooling and Freezing
* Cooling inhibits most microbial growth
* Freezing kills many microorganisms due to formation of ice crystals inside their cells
Boiling and cooking
High heat kills contaminating
microorganisms
Pasteurization
Exposes samples to a lower heat (usually 60 – 70 °C) for a shorter amount of time
* Kills off most of the problematic
pathogens
* Used to preserve heat-sensitive products such as milk and wine
Bio153
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