TrachyMicrobiomes
Microbiomes of ant castes implicate new microbial roles in the fungus-growing ant Trachymyrmex septentrionalis
To generate insights into such phenological changes in ant-associated bacterial microbiomes, we performed culture-dependent isolation and culture-independent 16S-amplicon 454-sequencing of T. septentrionalis nests collected between January and September 2009. For each nest, ant nest workers, outside workers, fungal gardens, chamber soil, and soil excavate were collected and when available we also collected reproductive male and female alates.  A total of 137 samples underwent culture-independent 454 sequencing.
Fungus-growing ants employ several defenses against diseases, including disease-suppressing microbial biofilms on their integument and in fungal gardens.  Here, we compare the phenology of microbiomes in natural nests of the temperate fungus-growing ant Trachymyrmex septentrionalis, using culture-dependent isolations and culture-independent 16S-amplicon 454-sequencing.  454-sequencing revealed diverse actinobacteria associated with ants, including most prominently Solirubrobacter (12.2-30.9% relative abundance), Pseudonocardia (3.5-42.0%), and Microlunatus (0.4-10.8%).  Bacterial abundances remained relatively constant in monthly surveys throughout the annual active period (late winter to late summer), except Pseudonocardia abundance declined in females during the reproductive phase.  Pseudonocardia species that occur abundantly on ants are phylogenetically different from those in gardens and soil, indicating ecological separation of these Pseudonocardia types.  Because the pathogen Escovopsis is not known to infect gardens of T. septentrionalis, the ant-associated microbes do not seem to function in Escovopsis suppression, but could protect against other diseases, help in nest sanitation, or serve unknown functions.