Lecture 9 Flashcards
Bacterial diversity
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
How are new species identified
Detect 16S rRNA genes in environmental samples to accelerate identification of new species
Proteobacteria
- 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
Cyanobacteria
- Gram negative
- Only bacterial photoautotroph which does oxygenic photosynthesis
- Ancestors of eukaryotic chloroplasts via endosymbiosis
Gram-positive bacteria
- 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)
Chlamydias
- ‘Gram negative’
- Obligate parasites, survival inside host cells
- No peptidoglycan cell wall
Spirochetes
- Gram negative
- Some are free-living, some symbiotic
- Borrelia burgdorferi, causative agent of Lyme disease, etc.
Lyme disease
- Caused by B. burgdorferi
- Bacteria carried by ticks
- debilitating arthritis, heart diseases, etc.
Symbiosis
two different species living together
in close relationship
Symbiont
(usually the smaller species) lives with
their host
Types of symbiotic relationship
- 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
Many bacteria are human
symbionts, co- existing on our ‘surface’
* Skin, mouth, respiratory tract, intestine, vagina, etc
Humans co-exist with numerous
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
Disease
disturbance in the normal functioning of an organism
Infectious disease:
any disease caused by a microorganism
Bacteria, eukaryotic protists, fungi and viruses are all known to have species who
cause diseases in humans
Members of Archaea have not been
conclusively associated with any
specific disease
Mycobacterium tuberculosis
Causative agent of tuberculosis
Halobacterium sp.
- Extremophile Archaea
- requires extreme amounts of salt in environment for survival
Pathogen
is a microorganism that causes a specific disease
Pathogenesis
is the process which a pathogen causes
the disease
Requirements of pathogenesis
- 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
How does Biofilm helps pathogenesis
- Secretion of capsule/slime layer forms structures to support bacterial communities to co-exist
- Helps with attachment and evasion of host defense
What are biofilms
collection of microorganisms that stick together and to a surface, forming a slimy layer