Project description:The nitrogen rich compound guanidine occurs widely in nature and is used by microbes as a nitrogen source, but microorganisms that grow on guanidine have not yet been discovered. Here we show that complete ammonia-oxidizing microbes (comammox), but no other known nitrifiers, encode homologues of a guanidinase and that the comammox isolate Nitrospira inopinata grows on guanidine as sole source of energy and reductant. Proteomics, kinetic enzyme characterization, and the crystal structure of the N. inopinata guanidinase homologue demonstrated that it is a bona fide guanidinase. Transcription of comammox guanidinases was induced in wastewater treatment plant microbiomes upon incubation with guanidine, and guanidine degradation was detected in these systems. The discovery of guanidine as a selective growth substrate for comammox shows a unique niche of these globally important nitrifiers and offers new options for their isolation as well as for targeted manipulation of nitrifier communities.
Project description:Eutrophication can lead to an uncontrollable increase in algal biomass, which has repercussions for the entire microbial and pelagic community. Studies have shown how nutrient enrichment affects microbial species succession, however details regarding the impact on community functionality are rare. Here, we applied a metaproteomic approach to investigate the functional changes to algal and bacterial communities, over time, in oligotrophic and eutrophic conditions, in freshwater microcosms. Samples were taken early during algal and cyanobacterial dominance and later under bacterial dominance. 1048 proteins, from the two treatments and two timepoints, were identified and quantified by their exponentially modified protein abundance index. In oligotrophic conditions, Bacteroidetes express extracellular hydrolases and Ton-B dependent receptors to degrade and transport high molecular weight compounds captured while attached to the phycosphere. Alpha- and Beta-proteobacteria were found to capture different substrates from algal exudate (carbohydrates and amino acids, respectively) suggesting resource partitioning to avoid direct competition. In eutrophic conditions, environmental adaptation proteins from cyanobacteria suggested better resilience compared to algae in a low carbon nutrient enriched environment. This study provides insight into differences in functional microbial processes between oligo- and eutrophic conditions at different timepoints and highlights how primary producers control bacterial resources in freshwater environments.
2016-08-01 | PXD004592 | Pride
Project description:The distributions of comammox Nitrospira
Project description:Aggression among group housed male mice continues to challenge laboratory animal researchers because mitigation strategies are generally applied at the cage level without a good understanding of how it affects the dominance hierarchy. Aggression is typically displayed by the dominant mouse, targeting lower ranking subordinates, thus strategies may be more successful if applied specifically to the dominant mouse. Unfortunately, dominance rank is often not assessed because of time intensive observations or tests. Several dominance measures have been developed, but none directly compared to home cage behavior in standard housing. This study assessed the convergent validity of three dominance measures (urinary darcin, tube test score, preputial gland to body length ratio) with wound severity and rankings based on home cage behavior, using factor analysis. Discriminant validity with open field measures was assessed to determine if tube test scores are independent from anxiety. Cages were equally split between SJL and albino C57BL/6 strains and group sizes of 3 or 5 (N=24). During the first week, home cage behavior was observed, and the dominance measures were recorded over the second week. After controlling for strain and group size, darcin and preputial ratio had strong loadings on the same factor as home cage ranking and were significant predictors of home cage ranking showing strong convergent validity. Tube test scores were not significantly impacted by open field data, showing discriminant validity. Social network analysis was also done to reveal that despotic power structures were prevalent, aggressors were typically more active and rested away from cage mates, and the amount of social investigation and aggression performed by an individual were highly correlated. Data from this study show that darcin and preputial ratio are representative of home cage aggression and provide further insight on individual behavior patterns in group housed male mice.
2021-01-21 | MSV000086740 | MassIVE
Project description:The distributions of comammox Nitrospira in taihu