Lecture 15 - Gram negative part 1 Flashcards
1
Q
Who are the Phylum Aquificae?
[Gram Neg]
A
- Thought to be deepest (oldest) branch of Bacteria
- Can be chemolithoautotroph
- Uses hydrogen, thiosulfite, and sulfur as electron donor
- Uses oxygen as electron acceptor
2
Q
Who are the Phylum Thermotogae?
[Gram Neg]
A
- Second deepest branch of Bacteria
- Best studied genus is Thermotoga
- Hyperthermophiles - grow in active geothermal areas
- Can be chemoheterotrophs
- Have functional glycolytic pathway
- Can grow anaerobically on carbohydrates and proteins digests.
3
Q
What does both Phylum Thermotogae and Phylum Aquificae have in common?
A
- Both are gram negative rods
- Both can be hyperthermophiles
4
Q
Who are the Deinococcus-Thermus?
[Gram Neg]
A
- Spherical or rod-shaped
- They are stained gram-positive but do not have typical gram-positive cell wall
- Plasma membrane has large amounts of palmitoleic acid rather than phosphatidylglycerol phospholipids
- Extraordinarily resistant to desiccation and radiation.
- Isolated from ground meat, feces, air, fresh water, and other sources, but natural habitat unknown.
- They have numerous genome repair mechanisms and can repair fragmented chromosomes within 12-24 hours.
5
Q
Phylum Chloroflexi are a group of gram negative photosynthetic bacteria. List their characteristics.
A
- Green nonsulfur bacteria
- Filamentous: gliding motility
- Has both photosynthetic and nonphotosynthetic members…..
- Chloroflexus - photosynthetic
- Herpetosiphon - nonphotosynthetic
- Thermophilic
-
Anoxygenic photosynthesis: does not use water as electron donor.
- Can grow aerobically as a chemoheterotroph
- Herpetosiphon isolated from fresh water and soil habitats…
6
Q
Phylum Chlorobi are a group of gram negative photosynthetic bacteria. List their characteristics.
A
- Green sulfur bacteria
- Obligately anaerobic photolithoautotrophs
- Reaction center bacteriochlorophyll located in plasma membrane
- Uses H2S, elemental sulfur and H2 as electron sources
- Elemental sulfur deposited outside cell.
- Morphologically diverse
- Rods, cocci, or vibrios; single cells, chains, or clusters.
- Have chlorosomes.
- Lack flagella, nonmotile
- Some have gas vesciles to adjust water depth for adequate light and H2S.
7
Q
What are chlorosomes?
A
- Ellipsoidal vesicles attached to plasma membrane
- Bounded by membrane that is not a normal lipid bilayer
- Contain accessory photosynthetic pigments
8
Q
What are Cyanobacteria?
A
- Photosynthetic prokaryotes with the ability to synthesize chlorophyll a
- Commonly referred to as blue-green algae, cyanophyta, cyanoprokarya, “slime”
- Amongst the earlist (first?) life on Earth
- Ecologically vital for a wide range of ecosystems
9
Q
List and describe the types of cells found in cyanobacteria.
A
-
Vegetative cells
- Flattened or coccoid
-
Heterocytes
- Site of nitrogen fixation
- Strictly anaerobic
- Environmentally induced
- Non-reversible transformation
-
Akinetes
- Function as resting cells to allow survival under adverse conditions
-
Baeocytes (aka endospores)
- Spores formed by internal division of vegetative cells
-
Exospores
- Spores cut off from one end of the parental cell
10
Q
Describe the ecology of cyanobacteria.
A
- Tolerant of environmental extremes
- Often are primary colonizers
- Can cause blooms in nutrient-rich ponds and lakes
- Some can produce toxins….
- Often form symbiotic relationships
- e.g., are phototrophic partner in most lichens
- e.g., symbionts with protozoa and fungi
- e.g., nitrogen-fixing species form associations with plants
11
Q
What’s so cool about the Phylum Planctomycetes?
[Gram neg]
A
- Spherical or oval, budding bacteria
- Lacks peptidoglycan
- Have crateriform structures (pits) in walls
- Most have life cycles in which sessile cells bud to produce motile swarmer cells
- They typically lack peptidoglycan
- Some species have nuclear body that is membrane bound
- Some species can attach to surfaces through a stalk and holdfast. These tend to be aquatic
12
Q
Every teenager dreads hearing the word chlamydia. But they don’t exactly know why chlamydia is a virulent STI agent. What makes Phylum Chlamydie so important to medical microbiologists?
A
- Nonmotile, coccoid, gram-negative bacteria
- Cell walls lack muramic acid and peptidoglycan
- Have very small genomes
- Obligate intracellular parasites with unique developmental cycle
- Found mostly in mammals and birds
- Some recently isolated from spiders, clams, and freshwater invertebrates
- Can secrete elementary bodies which are similar to outer membrane vesicles. Elementary bodies become reticulate bodies
13
Q
Describe the Chlamydial metabolism.
A
- Appear to be energy parasites, obtaining ATP from host
- Do have genes for substrate-level phosphorylation, electron transport, and oxidative phosphorylation.
- Reticulate bodies have biosynthetic capabilities when supplied precursors from host; can synthesize some amino acids
- Elementary bodies seem to be dormant forms
14
Q
What are some of the important pathogens belonging to Phylum Chlamydiae?
A
- C. trachomatis
- Infects humans and mice
- Causes trachoma, nongonococcal urethritis, and other diseases in humans
- C. psittaci
- Infects humans and many other animals
- Causes psittacosis in humans
- C. pneumoniae
- Common cause of human pneumonia
15
Q
Why do we care about Phylum Spirochaetes?
[Gram neg]
A
- Gram-negative bacteria with distinctive structure and motility
- Slender, long with flexible helical shape
- Creeping (crawling) motility due to a structure called an axial filament: complex of axial fibrils (periplasmic flagella). Axial fibrils rotate, causing corkscrew-shaped outer sheath to rotate and move cell through surrounding liquid. Spirochetes have multiple flagella. No ATP required to power the flagella because of PMF.
- Chemoheterotrophs
- Ecologically diverse
