Most dominant colonic bacteria is
Escherichia coli
Bacteroides
Clostridium
Veilonella
Bacteroids are the normal inhabitants of the intestine, respiratory, female genital tract. the normal flora of adult colon contains 96 to99% of anaerobes and only 1 to 4% of aerobes. Anaerobes - Bacteroides species, bifidobacteria, anaerobic lactobacilli, anaerobic streptococci. Ref: Baveja textbook of microbiology; 4th edition.
Bacteriology