Characterization and experimental manipulation of endosymbionts in the bed bug

It is widely reported that hematophagous arthropods require nutritional supplements from endosymbiotic microorganisms in order to survive and reproduce. In bed bugs, two or more microorganisms are housed in a specialized structure called the mycetome, but are also found in other tissues. The nature of the host-symbiont interaction has never been described. We used Denaturing Gradient Gel Electrophoresis (DGGE) in conjunction with 16S rDNA universal primers to qualitatively examine the endosymbiotic bacteria found in bed bugs. We then sequenced the resulting bands to confirm the identity and presence of two bacteria: Wolbachia sp. and an unnamed proteobacterium referred to in the literature as BLS (BEV-like symbiont). Another band, referred to as Symbiont 3, revealed a close rDNA sequence match to Wolbachia and may represent another strain.

We fed bugs blood containing incremental doses of the antibiotics tetracycline and rifamycin in an attempt to eliminate these symbionts. However, DGGE results revealed that tetracycline eliminated only Wolbachia, and rifamycin was effective in removing only Wolbachia and BLS. Tetracycline induced a severe reduction in oviposition. Analysis of first-instar offspring showed that progeny of rifamycin-treated adults had only Symbiont 3. Bed bugs treated with rifamycin showed no detrimental effects on fecundity, hatch rate, mortality, or defecation. Nymphs lacking these symbionts also had normal growth and molting patterns, suggesting no nutritional deficiency. A specific nutritive role for Symbiont 3 remains speculative until further experiments are completed.