Community structures of heterotrophic bacteria of copepod fecal pellets

The total and heterotrophic bacterial microflora of gut andfecal pellets of the copepod Temora stylifera was studied inthe coastal zone of the northwestern Mediterranean basin. Digestivetracts and feces were always found to contain bacteria. Withmean values close to 10¹¹ cells ml^–1and 10¹⁰ colony-formingunits (CFU) ml^–1, both total and heterotrophic communitiesfound in fecal pellets largely exceeded the corresponding bacterialmicroflora observed in surrounding seawater (10⁵ cells ml¹ and10³ CFU ml^–). In the same way, the frequency of dividingcells and mean cell volumes increased, respectively, from 3%and 0.12µm³ in seawater to >6% and 0.24 µm³ infecal pellets. The bacterial community structure was investigatedby carrying out 29 morphological and biochemical tests on 147isolated strains. Although Pseudomonas was always the most frequentlyencountered genus, the bacterial communities found in copepodfecal pellets clearly differ from those inhabiting seawater.Vibrio species, which were not detected in seawater microflora,were always present in fecal pellet communities. The close correspondenceobserved between the potential metabolic characteristics ofthe fecal bacterial communities isolated from a subantarcticdeposit feeder (Mytilus edulis) and from zooplankton in thisMediterranean study suggests that the fecal community differentiationis an even more general feature.