Diet does not drive bacterial community structure in the gut of litter-feeding cockroaches

While the gut microbiota of termites and its role in symbiotic digestion have been studied for decades, little is known about the bacteria colonizing the intestinal tract of cockroaches that degrade lignocellulosic matter. Here, we investigate the gut microbiota of three cockroach species that were fed on dried leaf litter, Ergaula capucina, Byrsotria sp., and Pycnoscelus surinamensis, and compare them to that of the previously investigated wood-feeding cockroaches Panesthia angustipennis and Salganea esakii. The physicochemical conditions in the gut of the litter-feeding species, determined using microsensors, differed only slightly from those reported for other cockroaches. All gut compartments were anoxic at the center and had a slightly acidic to neutral pH and variable, but slightly reducing conditions. By contrast, the localization of hydrogen accumulation in the crop, as previously shown in P. angustipennis, was here reproduced in Byrsotria sp., and strongly differs from data on omnivorous species. In all analyzed species, the microenvironmental conditions in the hindgut compartment were the strongest determinant of bacterial community structure. An extended comparison including other cockroaches and termites of diverse feeding groups revealed that most of the core taxa in the hindgut bacterial communities of cockroaches with a lignocellulosic diet were shared with other, omnivorous species, but differed strongly from those in wood-feeding higher termites.