Catechol 2,3-dioxygenase and other meta-cleavage catabolic pathway genes in the “anaerobic” termite gut spirochete Treponema primitia

Microorganisms have evolved a spectacular diversity of metabolisms, some of which allow them to overcome environmental constraints, utilize abundant but inaccessible resources, and drive nutrient cycling in various ecosystems. The termite hindgut microbial community is optimized to metabolize wood and in recent years, the in situ physiological and ecological functions of community members have been researched. Spirochetes are abundant in the termite gut and herein, putative aromatic meta-cleavage pathway genes typical of aerobic pseudomonads were located in genomes of homoacetogenic termite hindgut “anaerobes,” Treponema primitia str. ZAS-1 and ZAS-2. Phylogenetic analyses suggest the T. primitia catechol 2,3-dioxygenase and several other essential meta-pathway genes were acquired from an α-proteobacterium in the distant past to augment several genes T. primitia acquired from anaerobic firmicutes that do not directly catabolize aromatics but can contribute to the final pathway steps. Further, transcripts for each meta-pathway gene were expressed in strictly anaerobic cultures of T. primitia str. ZAS-2 indicative of constitutive pathway expression. Also, the addition of catechol + O_2 to T. primitia liquid cultures resulted in the transient accumulation of trace amounts of the yellow ring cleavage product, hydroxymuconic semialdehyde. This is the first evidence of aromatic ring cleavage in the phylum (division) Spirochetes. Results also support a possible role for T. primitia in termite hindgut O_2/lignin aromatic monomer metabolism. Potential O_2-dependent yet non-respiratory microbial metabolisms have heretofore been overlooked and warrant further investigation. These metabolisms could describe the degradation of plant-derived and other aromatics in microoxic environments, and contribute significantly to carbon turnover

Localizing transcripts to single cells suggests an important role of uncultured deltaproteobacteria in the termite gut hydrogen economy

Identifying microbes responsible for particular environmental functions is challenging, given that most environments contain an uncultivated microbial diversity. Here we combined approaches to identify bacteria expressing genes relevant to catabolite flow and to locate these genes within their environment, in this case the gut of a “lower,” wood-feeding termite. First, environmental transcriptomics revealed that 2 of the 23 formate dehydrogenase (FDH) genes known in the system accounted for slightly more than one-half of environmental transcripts. FDH is an essential enzyme of H_2 metabolism that is ultimately important for the assimilation of lignocellulose-derived energy by the insect. Second, single-cell PCR analysis revealed that two different bacterial types expressed these two transcripts. The most commonly transcribed FDH in situ is encoded by a previously unappreciated deltaproteobacterium, whereas the other FDH is spirochetal. Third, PCR analysis of fractionated gut contents demonstrated that these bacteria reside in different spatial niches; the spirochete is free-swimming, whereas the deltaproteobacterium associates with particulates. Fourth, the deltaproteobacteria expressing FDH were localized to protozoa via hybridization chain reaction-FISH, an approach for multiplexed, spatial mapping of mRNA and rRNA targets. These results underscore the importance of making direct vs. inference-based gene– species associations, and have implications in higher termites, the most successful termite lineage, in which protozoa have been lost from the gut community. Contrary to expectations, in higher termites, FDH genes related to those from the protozoan symbiont dominate, whereas most others were absent, suggesting that a successful gene variant can persist and flourish after a gut perturbation alters a major environmental niche

Cross-cutting principles for planetary health education

Since the 2015 launch of the Rockefeller Foundation Lancet Commission on planetary health,1 an enormous groundswell of interest in planetary health education has emerged across many disciplines, institutions, and geographical regions. Advancing these global efforts in planetary health education will equip the next generation of scholars to address crucial questions in this emerging field and support the development of a community of practice. To provide a foundation for the growing interest and efforts in this field, the Planetary Health Alliance has facilitated the first attempt to create a set of principles for planetary health education that intersect education at all levels, across all scales, and in all regions of the world—ie, a set of cross-cutting principles

acetaldehyde dehydrogenase original MUSCLE alignment.txt

acetaldehyde dehydrogenase original MUSCLE alignment.tx