Abstract:
The McMurdo Dry Valleys of Antarctica support
extensive yet cryptic microbial communities but little
evidence for ‘top-down’ herbivory control. A question
therefore arises as to how standing microbial biomass is
regulated. Here, we present results from a survey of soil and
rock microbial community metagenomes using the GeoChip
microarray that demonstrate antibiotic resistance and phage
infection are widespread. We interrogated a range of dry
valley locations from maritime to extreme inland sites.
Antibiotic resistance genes were identified in three categories:
beta-lactamases, tetracycline and vanomycin plus a
range of transporter genes. Frequency of recovery generally
reflected microbial diversity, with greatest abundance
among Halobacteria, Proteobacteria and the photosynthetic
bacteria (Chlorobi, Chloroflexi and Cyanobacteria). However,
no clear differences between locations and soil/rock
communities were apparent. Phage signals were also recovered
from all locations in soil and rock communities. The
Leviviridae, Myoviridae, Podoviridae and Siphoviridae were
ubiquitous . The Corticoviridae occurred only in moisturesufficient hyporheic soils, the Microviridae occurred only in
maritime and hyporheic sites and an unidentified group
within the order Caudovirales occurred only at dry inland
sites. We postulate that widespread antibiotic resistance
indicates potential inter-specific interaction and that phage
signals indicate possible ‘bottom-up’ trophic regulation in
the dry valleys.
