Lecture Five
 
 

GRAM – ve BACTERIA:



 

Facultative Anaerobes (The Enteric Bacteria)
Enterobacteriaceae
The habitat for most of these is the intestines of some sort of animal. But many can be found in soil and on plant material. All are fermentative (facultative anaerobes)
Important genera:
Salmonella The most common cause of gastro enteritis in Australia and has over 2000 species one of which is particularly dangerous (S. typhi cause typhoid fever)
Escherichia (E. coli) used as an indicator of faecal pollution because E. coli only occurs in faeces. It is usual harmless and represents about 10% of the bacteria found in the human intestine. Some varieties are weak pathogens ie. Only causing disease in vulnerable groups. The disease they cause in these vulnerable individuals can be vary serious eg Enteropathogenic E. coli ( EEC) causing traveller’s diarrhoea and E. coli O157:H7 which causes Haemolytic Uraemic Syndrome
Shigella has a few species that cause gastroenteritis as well as a real baddy (S. dysenteriae that causes bacillary dysentery and is closely related to E. coli)
Yersinia has a gastro causing species and a real baddy (Y. pestis causes plague)
Klebsiella (fixes N2 and can cause pneumonia)
Serratia is used to look for faecal pollution in marine environments
Erwinia (live on plants - some plant pathogens)
Vibrio (vib = L. for whip mark), Has a different morphology and causes fish diseases and gastro in humans who eat raw fish.
Photobacterium (bioluminescent)
Aeromonas (includes fish pathogens).
 Being facultative anaerobes they are capable of living dual lives. They can live in their anaerobic environments like the gut and aerobically in waters , soil and on food surfaces.
 
 

Strict Aerobes

Pseudomonads
Pseudomonas - polar flagella and oxidase positive.
A very large genus that is now being broken up into many different genera.
Fluorescent Pseudomonads
P. putida
P. aeruginosa (flowers and burn patients)
These have fluorescent pigments are iron chelating compounds (siderophores)
and cause slime and discolouration of foods as well as putrid odours
Campylobacter A fastidious oxidase positive non-fermentative spiral (curved or corkscrew shaped) bacteria with a very long flagella (three times longer than the cell body) Most common cause of reported gastroenteritis cases (or equal to Salmonella)
C. fetus causes abortions in cattle Some species have been renamed as Helicobacter H.pylori is a resident of the stomach and duodenum and can cause ulcers and chronic gastritis and cancer of the stomach.
 

The End

Prepared by Barry Brazier