Colman, D. | Search bioRxiv

bioRxiv2024

Environmental controls on crenarchaeol distributions in hydrothermal springs

Thermophilic archaea synthesize cellular membranes composed primarily of isoprenoid glycerol dibiphytanyl glycerol tetraethers (iGDGTs). Cells can adjust the packing of their lipids by increasing the number of cyclopentyl rings during lipid synthesis, thereby decreasing membrane permeability and fluidity to maintain cellular function at high temperature, acidic pH, or nutrient limitation. Archaea of the class Nitrososphaeria synthesize an iGDGT, crenarchaeol, with four cyclopentyl rings and a cyclohexyl ring, the function of which is unknown. Structural modeling suggests the cyclohexyl ring may increase membrane fluidity, potentially optimizing membranes for mesophilic conditions. To begin to investigate this hypothesis, iGDGT composition was quantified in forty-one thermal springs in Yellowstone National Park (YNP), USA, and contextualized within a global thermal spring iGDGT compilation with pH values of 1.1 to 10.1 and temperatures of 16 to 95{degrees}C. pH was the strongest predictor of both crenarchaeol relative abundance and the number of cyclopentyl rings per iGDGT. Crenarchaeol relative abundance exhibited a nonlinear relationship with pH and temperature, with highest relative abundances at pH 7.4 and 46{degrees}C, then decreasing above and below these values. These observations are consistent with the hypothesis that the cyclohexyl ring of crenarchaeol optimizes archaeal cellular membranes for circumneutral and moderate temperature environmental conditions. ImportanceArchaea change the composition of their membrane lipids to alter the fluidity of their membranes to maintain cell homeostasis when confronted with environmental stress. Some archaea of the class Nitrososphaeria produce a lipid, crenarchaeol, with a unique six-membered ring, the effect of which on archaeal membrane dynamics remains unknown. In this study, we identify pH as the most important geochemical variable for archaeal membrane response in Yellowstone National Park thermal springs. In addition, the lipid distributions indicate that crenarchaeol production is highest in circumneutral and mesophilic environments. The YNP results are supported by similar trends across global thermal springs.

microbiology↗

bioRxiv2024

Challenging the impact of consortium diversity on bioaugmentation efficiency and native 1 bacterial community structure in a freshly PAH-contaminated soil

Polycyclic aromatic hydrocarbons (PAHs) are priority pollutants. We studied the effect of bioaugmentation with three allochthonous bacterial consortia with increasing diversity, SC AMBk, SC1 and SC4, in the structure and functionality of an acutely PAH-contaminated soil microbiome. The PAH supplementation increased the resource availability and the inocula were able to: efficiently degrade the PAHs supplemented after 15 days of incubation, become temporary established, and modify the number of total interactions with soil residents. Sphingobium and Burkholderia, both member of inoculants, were the major contributors to KO linked to degradation and to differentially abundant genera in inoculated microcosms, indicating their competitiveness in the soil. Bioaugmentation efficiency relayed on them, while further degradation, could be carried out by native microorganism. This is the one of the first works which applied three inocula, designed from naturally occurring bacteria and study their effect on the soil native community through the ANCOM-BC. We revealed that when a resource that can be use by the inoculant is added to the soil, it is not necessary a high-diversity inoculant to interact with native community and establish itself. This result has implications in the design of microbiome engineering for bioremediation processes

microbiology↗