The gut microbiota of the blattid cockroach Shelfordella lateralis
This thesis focuses on the conditions prevailing in the gut compartments of the cockroach Shelfordella lateralis and gives new insights into the composition of associated bacterial, archaeal and eukaryotic microorganisms. While the symbiotic gut microbiota of termites has been focused by many studie...
Saved in:
Main Author: | |
---|---|
Contributors: | |
Format: | Doctoral Thesis |
Language: | English |
Published: |
Philipps-Universität Marburg
2011
|
Subjects: | |
Online Access: | PDF Full Text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | This thesis focuses on the conditions prevailing in the gut compartments of the cockroach Shelfordella lateralis and gives new insights into the composition of associated bacterial, archaeal and eukaryotic microorganisms. While the symbiotic gut microbiota of termites has been focused by many studies due to its cellulolytic function, the gut microbiota of the others members of the order Dictyoptera, cockroaches and mantis, remained mostly unexamined. Therefore, the gut microbiota of the blattid cockroach S. lateralis was characterized via molecular techniques, including a deep pyrosequencing approach.
Crop and midgut were in all individuals mainly colonised by lactic acid bacteria and Bacteroidetes. This was also in agreement with the high lactate concentrations found in these compartments, which was consistent over all analysed individuals. By contrast, the bacterial composition of the hindgut, including colon and rectum, differed strongly between individuals. The colon, as hotspot of bacterial diversity, harboured mainly members of Bacteroidetes, Firmicutes as well as δ-Proteobacteria. A large proportion of clones belonged to groups isolated from anaerobic environments, for example Clostridia, reflecting the anoxic center detected within each gut compartment. Spirochaetes and Fibrobacteres, assumed to carry out cellulose digestion in higher termites, were not detected via Sanger sequencing, but showed a low abundance in pyrosequencing approach, reflecting the omnivorous diet of S. lateralis. A third of clones clustered with sequences previously obtained from the termite gut, reflecting the common evolutionary history of cockroaches and termites.
Different diets (chicken feed as balanced, soy as protein-rich and bran and bran- cellulose as fiber-rich diets) were used to examine the influence of diet. A possible dietary impact was masked by the large degree of individual variation. In ordination analysis, the colonal fingerprinting profiles of individuals showed a tendency to cluster after diets, but the effect of housing environment was overlaid, indicating that the available pool of bacteria for gut microbiota acquisition plays a superior role. Pyrosequencing analysis detected no differences in gut microbial composition, but found nine additional phyla, which were less abundant in all diets and so counted to the rare phyla. Analysis of bacterial community structure by terminal-restriction-fragment length polymorphism and 454 pyrotagsequencing of 16S rRNA genes revealed a high individual variability but little impact of diet, suggesting that cockroaches are able to maintain a gut microbiota that is insensitive to dietary shifts. This was also supported by the results that volatile fatty acid concentrations were not significantly changed by different diets.
Methanogenesis in arthropods is limited in occurrence to few taxa, namely termites, scarab beetles, millipedes and cockroaches. In this study, most individuals emitted methane. Some individuals emitted only detectable amounts of methane after stimulation with hydrogen. Two species of methanogenic archaea were found in the hindgut, namely Methanomicrococcus blatticola and an uncultivated Methanobrevibacter. The relative abundance of both types was quite variable in cockroaches with and without methane emission. Ciliates observed in the cockroach hindgut belonged to Nyctotherus ovalis and were associated endosymbiotic with uncultivated Methanobrevibacter. Diet had no impact on methane emission rates, but hydrogen was significantly higher in individuals fed a high fiber diet. Chicken feed fed individuals had the highest increase in methane emission after hydrogen stimulation, whereas individuals fed a high fiber diet showed a low or negative response of the methane emission rate. In all different diets, individuals not capable of methane emission were found. |
---|---|
DOI: | 10.17192/z2012.0086 |