Editors' ChoiceDevelopmental Biology

Bacteria Boost Reproduction

Sci. Signal.  22 Nov 2011:
Vol. 4, Issue 200, pp. ec327
DOI: 10.1126/scisignal.4200ec327

Invertebrates infected with maternally transmitted intracellular bacteria of the genus Wolbachia reproduce more successfully than do uninfected individuals because the bacteria alter host reproduction by, for example, skewing sex ratios to favor females, increasing female fecundity (reproductive ability), or preventing uninfected males from successfully mating with infected females. Fast et al. report that bacteria accumulated in the germline stem cell (GSC) niche of Drosophila mauritiana infected with the Wolbachia wMau strain and caused infected females to produce more eggs than did noninfected females. In contrast, bacteria did not accumulate in the GSC niche of wMau-infected D. melanogaster, highlighting that the phenotypic effects of Wolbachia infection vary with different combinations of host species and bacterial strain. wMau infection in D. mauritiana was associated with an increase in GSC proliferation, as indicated by three different methods of marking dividing cells. The amount of bacteria present in GSCs positively correlated with the observed increase in mitotic activity. However, the increase in proliferation only accounted for about half of the observed increase in egg production; the remainder resulted from wMau-induced inhibition of apoptosis in developing germaria, which are groups of undifferentiated cells that give rise to the oocyte and to the germline-derived nurse cells and the somatic cells that support oocyte development. The mechanistic basis of these effects on proliferation and apoptosis was not determined but highlights the cellular basis of how infection leads to increased fecundity in at least one host-bacteria combination. In some host species, Wolbachia infection is considered to be symbiotic rather than parasitic, and many important insects that cause or transmit human disease harbor Wolbachia, so understanding how these infections affect host reproductive success may offer key insights into strategies for controlling populations of disease-causing insects.

E. M. Fast, M. E. Toomey, K. Panaram, D. Desjardins, E. D. Kolaczyk, H. M. Frydman, Wolbachia enhance Drosophila stem cell proliferation and target the germline stem cell niche. Science 334, 990–992 (2011). [Abstract] [Full Text]