T. Thimm et al., THE GUT OF THE SOIL MICROARTHROPOD FOLSOMIA-CANDIDA (COLLEMBOLA) IS AFREQUENTLY CHANGEABLE BUT SELECTIVE HABITAT AND A VECTOR FOR MICROORGANISMS, Applied and environmental microbiology, 64(7), 1998, pp. 2660-2669
Interaction potentials between soil microarthropods and microorganisms
were investigated with Folsomia candida (Insecta, Collembola) in micr
ocosm laboratory experiments. Microscopic analysis revealed that the v
olumes of the simple, rod-shaped guts of adult specimens varied with t
heir feeding activity, from 0.7 to 11.2 nl, A dense layer of bacterial
cells, associated with the peritrophic membrane, was detected in the
midgut by scanning electron microscopy. Depending on the molting stage
, which occurred at intervals of approximately 4 days, numbers of hete
rotrophic, aerobic gut bacteria changed from 4.9 x 10(2) to 2.3 x 10(6
) CFU per specimen. A total of 11 different taxonomic bacterial groups
and the filamentous fungus Acremonium charticola were isolated from t
he guts of five F. candida specimens. The most abundant isolate was re
lated to Erwinia amylovora (96.2% DNA sequence similarity to its 16S r
RNA gene). F, candida preferred to feed on Pseudomonas putida and thre
e indigenous gut isolates rather than eight different type culture str
ains. When luciferase reporter gene-tagged bacterial strains were puls
e fed to F. candida, gut isolates were continuously shed for 8 days to
several weeks but Escherichia coli HB101 was shed for only 1 day. Rat
ios of ingested to released bacterial cells demonstrated that populati
ons of nonindigenous gut bacteria like Sinorhizobium meliloti L33 and
E. coli HB101 were reduced by more than 4 orders of magnitude but that
the population of gut isolate Alcaligenes faecalis HR4 was reduced on
ly 500-fold. This work demonstrates that F, candida represents a frequ
ently changeable but selective habitat for bacteria in terrestrial env
ironments and that microarthropods have to be considered factors that
modify soil microbial communities.