Cockroaches, like most organisms, have microorganisms that colonize the gut. What do the microorganisms do and what difference do they make?
Gnotobiotic cockroaches (cockroaches reared in a sterile environment are a potentially useful model system for answering these questions. Cockroaches package their eggs in a case called an ootheca. The ootheca can be surface sterilized and placed in a sterile environment. Cockroaches reared in the manner will lack gut microorganisms.
To start exploring these questions, a group of scientists* reared a cockroach species, Shelfordella lateralis in a sterile environment. The cockroaches can survive under aseptic conditions. Gut microorganisms may be helpful but are not necessary. Colonization of the cockroach gut by 2 bacteria, one a facultative anaerobe, the other an obligate anaerobe was studied. The bacteria colonized the hindgut but not other parts of the digestive system. They concluded that only the hindgut is a suitable environment for colonization. This fits with the observations that bacteria are most prevalent in the hindguts of cockroaches reared under natural conditions. The study found some changes in metabolism and possibly nutrition. Germ free cockroaches do not accumulate acetate in the gut as do the conventionally reared cockroaches. This study demonstrates that the cockroach can be a useful model system for studies where manipulation of gut fauna is required.
*Tegtmeier D, Thompson CL, Schauer C, Brune A. 2016. Oxygen affects gut bacterial colonization and metabolic activities in a gnotobiotic cockroach model. Appl Environ Microbiol 82:1080 –1089. doi:10.1128/AEM.03130-15.