Lec 6: Diversity of Gram -ve bacteria

Question 1

Gram -ve bacteria groups

Answer 1

Based on 16s rRNA studies

Non-Proteobacteria

Proteobacteria

Question 2

Green sulphur bacteria (phylum chlorobi)

Answer 2

Non-proteobacteria

Photosynthetic bacteria

Anoxygenic photosynthesis (do not evolve O2)

Deposit sulphur granules outside cell

Chromosomes contain photosynthetic pigments

Net-like structure

Question 3

Phylum Cyanobacteria

Answer 3

Non-proteobacteria

Photosynthetic bacteria

Largest, most diverse group of photosynthetic

Oxygen photosynthesis (evolve O2)

Development of life on earth: endosymbiosis of cyanobacteria evolved into chloroplast

Unicellular or filaments: vary in appearance

Thylakoid membrane carries our photosynthesis

Some have heterocysts (specialised cells. Fix N2 -> convert to NH3 to build AA)

Some develop into heterocysts if no nitrate or ammonia available

In most waters, soils

Can form ‘blooms’. Fertiliser allows rapid growth -> growth of chemoheterotrophic bacteria -> deplete O2 -> kill fish

May produce toxins -> kill livestock and other animals that drink water

Question 4

Genus Chlamydia

Answer 4

Phylum Chlamydiae

Non-proteobacteria

Gram -ve cocci

Obligate intracellular parasites (reproduce only in host cell) of mammals, birds

Question 5

Chlamydia trachomatis

Answer 5

Phylum Chlamydiae

Trachoma (bacterial infection)

Most common cause of preventable blindness in humans

Question 6

Phylum Spirochaetes

Answer 6

Non-proteobacteria

Gram -ve

Flexible helical cells

Axial fibrils (periplasmic flagella) -> corkscrew like motility through liquids and crawling on solid media

Question 7

Treponema pallidum

Answer 7

Phylum Spirochaetes

Cause of syphilis (contagious STD)

Question 8

Proteobacteria

Answer 8

Largest, most diverse group of bacteria

16s sequencing -> 5 subgroups (alpha, beta, gamma, delta, epsilon

Sometimes called purple bacteria (purple photosynthetic bacteria in alpha, beta and gamma)

Question 9

Alpha proteobacteria

Answer 9

Most oligotrophic: live in low nutrient environment

Some with distinctive morphology

Some pathogens

Some with unusual metabolic modes

Some photosynthetic bacteria

Include world’s most abundant group of bacteria

Question 10

Genus Caulobacter

Answer 10

Alpha proteobacteria

Gram -ve

Have a prostheca or stalk -> attachment to surfaces and nutrient uptake

Oligotrophs

In marine & fresh water, soil

Question 11

Genus Rickettsia

Answer 11

Gram -ve

Small rods, cocci or pleiomorphic

Obligate intracellular parasites

Question 12

Rickettsia prowazekii

Answer 12

Alpha

Typhus: high fever, rash, stupor

Question 13

Genus Rhizobium

Answer 13

Alpha

Gram -ve rods

Aerobic, motile

Infect roots of leguminous plants

Form root nodules: plant & bacteria symbiotic relationship. Bacteria fix (reduce) N2 to NH3 -> N available to plant host

Question 14

Genus agrobacterium

Answer 14

Alpha

Cause crown gall tumours in plants

Cancer causing bacterium

Same family as Rhizobium, both

Question 15

Genus Neisseria

Answer 15

Beta proteobacteria

Gram -ve

Aerobic diplococci

Inhabit mucus membranes of mammals

Question 16

Neisseria meningitidis

Answer 16

Cause of meningitis (inflammation of brain or spinal cord)

In nose or throat

Question 17

Neisseria gonorrhoeae

Answer 17

Cause gonorrhoea (STD)

Question 18

Gamma proteobacteria

Answer 18

Largest subgroup of proteobacteria

Some photosynthetic bacteria

Facultatively anaerobic chemoheterotrophs

Aerobic chemoheterotrophs

Question 19

Genus Pseudomonas

Answer 19

Gamma

Gram -ve

Aerobic respiration

Motile with 1 or more polar flagella

In soil & water

Many degrade wide range of organic substrates

Important in medicine, industry & environment

Question 20

Pseudomonas aeruginosa

Answer 20

Infects people with lowered resistance, burns, wounds, and has high antibiotic resistance

Question 21

Genus Vibrio

Answer 21

Gamma

Gram -ve

Curved rods (comma shaped)

Facultative anaerobes

Aquatic, marine habitats

Other species cause fish diseases

Question 22

Vibrio cholerae

Answer 22

Cholera: watery profuse diarrhoea

Question 23

Family: enterobacteriaceae

Answer 23

Gram -ve

Gamma

Straight rods

Facultative anaerobes

Simple nutritional requirements (ferment glucose & other carbohydrates)

Motile with peritrichous flagella (uniformly distributed over body surface)

Inhabit intestinal tracts

Question 24

Genus Escherichia

Answer 24

Family Enterobacteriaceae

Common inhabitant of human gastrointestinal tract

Commensal (symbiotic relationship)

Strains cause: gastroenteritis (traveller’s diarrhoea), urinary tract infections, haemolytic uraemic syndrome -> kidney failure

Question 25

Genus Salmonella

Answer 25

Family Enterobacteriaceae

Salmonella enterica: common cause of food poisoning or Gastroenteritis

Salmonella typhi -> typhoid (fever, epidemics). Typhoid Mary

Question 26

Genus Shigella

Answer 26

Family Enterobacteriaceae

Dysentery, shigellosis

E.g. Shigella dysenteriae

Question 27

Genus Klebsiella

Answer 27

Family Enterobacteriaceae

Pneumonia

E.g Klebsiella pneumoniae

Question 28

Genus Yersinia

Answer 28

E.g Yersinia Pestis

Plague/Black Death

Epidemics in Middle Ages

Flea vector: enlarged lymph nodes (buboes -> bubonic plague)

Sporadic

Question 29

Genus Bdellovibrio

Answer 29

Delta

Aerobic

Gram -ve

Motile

Curved rods

Prey on other gram -ve bacteria: collide violently with prey (flagella rotates) -> hole through cell wall with help of enzymes

Grows into filaments under cell wall

Question 30

Genus Helicobacter

Answer 30

Epsilon

Gram -ve

Microaerophilic (need oxygen, poisoned by high conc of oxygen)

Helical cell

Stomach and small intestine

Question 31

Helicobacter pylori

Answer 31

Epsilon

Human pathogen

Gastritis, peptic ulcer, gastric cancer

Question 32

Genus Campylobacter

Answer 32

Epsilon

Cause of gastroenteritis