Biology Reference
In-Depth Information
Husseneder (2010)
provided a review of the roles symbionts play in termite
nutrition in subterranean termites, especially
Reticulitermes
and
Coptotermes
.
Within the subterranean termites, the protozoa are involved in cellulose or
hemicellulose digestion and acetogenesis, while some bacteria produce vita-
mins, some bacteria are nitrogen-fixing and uric-acid degraders, others are
cellulolytic, some lactic acid bacteria are fermentative, others are acetogenic
CO
2
-reducing, whereas the Archaea are methanogenic. In addition, yeasts and
fungi are thought to be important, perhaps as a direct source of food and by
modifying wood.
Husseneder (2010)
pointed out that the mutualistic relation-
ship of termites with their symbionts may be one of the important factors in
allowing termites to have a social life style because each worker termite must
acquire an inoculum of symbionts from parents or nestmates after hatching and
after each molt so that parental care, group living, and overlapping generations
are needed, setting the stage for termites to become social.
Warnecke et al. (2007)
conducted a metagenomic and functional analysis
of hindgut microorganisms in a wood-feeding higher termite (which does not
have hindgut flagellate protozoa, which produce cellulases and hemicellulases
in the lower termites). DNA was obtained from the largest hindgut compart-
ment that contained bacteria and then analyzed by cloning and sequencing all
DNA. Because the bacterial community was large, only genes could be assem-
bled (rather than whole microbial genomes). The genes analyzed are of interest
to biotechnology because some may be used to produce biofuels from wood.
Termite symbionts also are of interest because termites are important in carbon
turnover in the environment.
Omnivorous cockroaches also have gut microbial communities, but the associa-
tions are less interdependent than those of termites. As in termites, the gut micro-
bial communities in cockroaches anaerobically degrade plant polymers and include
hydrogen-consuming bacteria, especially methanogens. The densities of these
microorganisms can be enormous; for example 5
×
10
12
bacteria/ml were found in
the hindgut of the cockroach
Periplaneta americana
(
Cazemier et al. 1997
).
4.12.4.2
Rhagoletis
Symbionts
A less intimate relationship between microbial genomes and insects is rep-
resented by the relationship between
Enterobacter agglomerans
, found in
the gut of the apple maggot
Rhagoletis pomonella
(
Lauzon et al. 2000
).
Enterobacteriaceae are the most common microorganisms associated with the
apple maggot in the gut and female reproductive organs, and it seems the flies
use the bacteria for some vital function(s) (
Lauzon et al. 1998
). In addition to
E. agglomerans
,
Klebsiella oxytoca
is found in the gut of
R. pomonella
, and both
