Microbial aspects of the cockroach hindgut

Area of Science:

• Microbiology
• Insect Biology
• Biochemistry

Background:

• Cockroach hindgut microbiota plays a crucial role in insect physiology.
• It differs from the hindgut microbiota of cellulose-dependent insects like termites.
• The midgut pH of Eublaberus posticus is not highly alkaline, suggesting a different nutritional role for its microbiota.

Purpose of the Study:

• To investigate the complex microbiota of the Eublaberus posticus hindgut.
• To characterize the chemical and microbial composition of distinct hindgut regions.
• To understand the impact of antibiotic treatment on hindgut structure and function.

Main Methods:

• Microbial isolation and characterization using dilution series on nonselective media.
• Measurement of methane production in adult Eublaberus posticus.
• Chemical analysis (ferrous and sulfide ions) and X-ray microprobe analysis of hindgut deposits.
• Electron microscopy to examine hindgut tissue structure.
• Metronidazole treatment to observe effects on hindgut differentiation.

Main Results:

• The hindgut is highly methanogenic, producing 10-25 mumol of methane per hour.
• Obligate anaerobes significantly outnumbered facultative anaerobes (100:1 ratio).
• Common facultative isolates include Klebsiella oxytoca, Citrobacter freundii, and Enterobacter agglomerans.
• A unique black region of the hindgut contains high concentrations of ferrous and sulfide ions, with deposits of iron, sulfur, copper, aluminum, and chromium.
• Metronidazole treatment led to dedifferentiation of hindgut regions.

Conclusions:

• The Eublaberus posticus hindgut possesses a specialized, highly active anaerobic microbiota.
• The black hindgut region is characterized by unique microbial and mineralogical features, likely involving iron and sulfur metabolism.
• Antibiotic treatment disrupts the normal hindgut structure, highlighting the importance of the microbiota in maintaining tissue differentiation.