Contribution of the colon and colonic bacterial flora to metabolism and development of the American cockroach Periplaneta americana L

An examination of profiles of volatile fatty acids (VFAs) and methane as end products of bacterial metabolism was used to assess the physiological significance of the colon and colonic anaerobic bacterial microflora during development of the American cockroach Periplaneta americana. The effects of reducing intestinal bacterial populations with an antibiotic, metronidazole, were evaluated by measuring VFAs concentrations, cockroach weight gain and development time (the length of nymphal period). Supplementary feeding of VFAs to treated animals was also evaluated. During normal development VFAs concentrations peaked during the first thirty days, then diminished slightly and remained relatively stable. Metronidazole treatment reduced bacterial populations in the colon, significantly lowered VFAs concentrations, reduced cockroach weight gain and extended the development time. Supplementary feeding of VFAs partially compensated for the effects of the antibiotic treatment (as measured by cockroach weight gain and development time). These results suggest a significant contribution of bacterial volatile fatty acids to cockroach metabolism, especially during the insect growth period. The significance of the colon as the major site of bacterial colonization is also discussed. Copyright (C) 1996 Elsevier Science Ltd