BACTERIAL COMMUNITIES ASSOCIATED WITH SOIL INVERTEBRATES

The effect of the soil diplopod Pachyiulus flavipes and the compost ea rthworm Eisenia fetida on communities of saprotrophic bacteria associa ted with their food, digestive tracts, and excrement was studied by me ans of plating on selective media and luminescence microscopy. The inv ertebrates were shown to stimulate the development of natural populati ons of soil saprotrophic bacteria passing through their,out: in fresh excrement, the total number of bacteria may increase by more than an o rder of magnitude. The number of streptomycin-resistant bacterial stra ins of Pseudomonas sp. and Promicromonospora citrea was 2 to 30 times greater in diplopod and earthworm excrement than in their food preinoc ulated with these bacteria. Depending on the composition of the predom inating bacteria, the communities associated with the diplopod and ear thworm.,out were divided into two types: those inhabiting the inner su rface of the gut wall and those developing in the contents of the gut. Gram-negative facultative anaerobes of the families Enterobacteriacea e and Vibrionaceae predominated in the gut-wall community; the gut-con tents community was represented by transiting bacteria, whose variety depended on the composition of bacteria in the food. The number of bac teria increased in the direction from the foregut to the hindgut, as w as particularly characteristic of the gut-contents community. In milli pede and earthworm excrement, the number of bacteria increased mostly due to gram-negative aerobes.