Agriculture Reference
In-Depth Information
a relatively slow doubling time (10-15 hours at ~23ºC), suggests an oligotrophic
lifestyle. Several of these strains produce a carotenoid pigment that is thought to
protect against oxidative stress when exposed to ambient O 2 concentrations. The
need for its production in ambient atmospheres suggests a sensitivity to O 2 that
would explain optimal growth rates under reduced O 2 atmospheres. The optimal
growth of these Acidobacteria under slightly acidic pH and low O 2 concentrations,
conditions commonly observed in many soils, is consistent with their widespread
distribution and abundance in soils.
The strains in one collection from KBS LTER are sufficiently similar, but dis-
tinct enough from previously named Acidobacteria, to warrant creation of a new
genus, Terriglobus. T.  roseus —the pigment-producing strain—has been defined
as the type species of the genus (Eichorst et  al. 2007). Studies are under way
to explore the role of the extensive extracellular polysaccharide produced by
Terriglobus strains (Fig. 6.7) in the formation of soil aggregates and to document
the capacity of the strains to degrade complex plant polymers.
The characterization of microbes in culture is a time-intensive endeavor that has
faded in popularity as access to molecular approaches has widened. As a result,
half of the 70+ known bacterial phyla have been identified solely from rRNA gene
sequences (Pace 2009), making it difficult to draw inferences about their genetics,
physiology, or ecology. The study of single cells (including deriving their complete
genome sequences) offers an intriguing new possibility for advancing our knowl-
edge of microbial physiology and the lifestyle trade-offs that underlie the distribu-
tion and activities of bacteria in nature.
Figure  6.7 . A  scanning electron micrograph of an isolate of the phylum Acidobacterium
revealing an extensive extracellular polysaccharide matrix that may be important in the for-
mation of soil aggregates. From Eichorst et al. (2007).
Search WWH ::




Custom Search