Bacterial preferences of the bacterivorous soil nematode Cephalobus brevicauda (Cephalobidae): Effect of bacterial type and size

SummaryCell size and type may affect availability of bacteria for consumption by bacterivorous nematodes in the soil and in culture. This study explored the bacterial preferences of the bacterivorous soil nematode Cephalobus brevicauda (Cephalobidae) by comparing bacteria isolated directly from soil, from commercial bacterial biological control agents, and from in vitro soil nematode cultures. The 16S rRNA sequences of bacterial isolates were compared to known sequences to identify phylogenetic affiliations. Bacterial preference of the nematode was observed by counting the number of Cephalobus brevicauda that were attracted to paired bacteria in a bioassay. Additionally, the reproductive output of single females reared on the bacteria was recorded. An attraction index established that Cephalobus brevicauda preferred Gram-negative, small-celled bacteria; however, Gram-positive bacteria supported maximum reproductive success. Bacterial biocontrol agents had no negative effects on reproduction, but Cephalobus brevicauda always preferred bacteria other than Dipel® (Bacillus thuringiensis ssp. kurstaki), in the bacterial preference assay.