Isolation of naturally associated bacteria of necromenic Pristionchus nematodes and fitness consequences.
Nematodes and bacteria are major components of the soil ecosystem. Many nematodes use bacteria for food, whereas others evolved specialized bacterial interactions ranging from mutualism to parasitism. Little is known about the biological mechanisms by which nematode-bacterial interactions are achieved, largely because in the laboratory nematodes are often cultured under artificial conditions. We investigated the bacterial interactions of nematodes from the genus Pristionchus that have a strong association with scarab beetles. Pristionchus has a different feeding strategy than Caenorhabditis and meta-genomic 16S sequence analysis of Pristionchus individuals showed a diversity of living bacteria within the nematode gut and on the nematode cuticle. Twenty-three different bacterial strains were isolated from three Pristionchus-beetle associations and were used to study nematode-bacterial interactions under controlled laboratory conditions. We show a continuum of bacterial interactions from dissemination, to reduction in brood size and nematode mortality caused by bacteria derived from insect hosts. Olfactory discrimination experiments show distinct chemoattraction and fitness profiles of Pristionchus nematodes when exposed to different bacteria. For example, Pristionchus pacificus avoids Serratia marcescens possibly because of pathogenicity. Also, P. pacificus avoids Bacillus thuringiensis and insect pathogenic bacteria but is resistant to the human pathogens Staphylococcus aureus and Pseudomonas aeruginosa, unlike Caenorhabditis elegans. Pristionchus specifically recognize and respond to bacteria that cause ill health. Bringing the nematode-bacterial interaction into the laboratory allows detailed functional studies, including the genetic manipulation of the interaction in both nematodes and bacteria.
Rae
Robbie
R
Max-Planck Institute for Developmental Biology, Department for Evolutionary Biology, Spemannstrasse 37, D-72076 Tübingen, Germany.
Riebesell
Metta
M
Dinkelacker
Iris
I
Wang
Qiong
Q
Herrmann
Matthias
M
Weller
Andreas M
AM
Dieterich
Christoph
C
Sommer
Ralf J
RJ
D000704:Analysis of Variance; D000818:Animals; D001419:Bacteria / Q000235:genetics* / Q000472:pathogenicity; D002633:Chemotaxis / Q000502:physiology; D001517:Coleoptera / Q000382:microbiology* / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D004064:Digestive System / Q000382:microbiology; D020387:Food Chain; D023281:Genomics / Q000379:methods; D009348:Nematoda / Q000033:anatomy & histology / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012903:Smell / Q000502:physiology; D013045:Species Specificity; D016019:Survival Analysis; D013559:Symbiosis
D017931:DNA Primers; D012336:RNA, Ribosomal, 16S