Biology subjects

Angenent, L. T.

Publications and source records attributed to Angenent, L. T..

4 recordsLinked to original sources

bioRxiv2020

The short-term effect of residential home energy retrofits on indoor air quality and microbial exposure: a case-control study

Weatherization of residential homes is a popular retrofit procedure to improve the energy efficiency of older homes by reducing building leakage. It is a vital tool in the fight against climate change. Several studies have evaluated the effect of weatherization on indoor pollutants such as formaldehyde and radon, but few studies have evaluated the effect of weatherization on indoor particulates and microbial exposure. In this study, we compared the effect of change in building leakage on indoor pollutants and bacterial communities in weatherized compared to non-weatherized single-family residential homes in New York State. Nine weatherized and eleven non-weatherized single-family homes in Tompkins County, New York were sampled twice: before and after the weatherization procedures for case homes, and at least 3 months apart for control homes that were not weatherized. We found a significant increase in both indoor-outdoor temperature ratio and living-area- and basement-radon levels of weatherized homes compared to control homes. The indoor-outdoor relative humidity ratio significantly decreased in weatherized compared to control homes. The indoor microbiome also became less similar to the outdoor community after weatherization. Compared to the changes in ventilation rate, temperature, relative humidity, and occupancy, the change in season was a more predictive measure of indoor bacterial concentration. Ventilation rate reduction from weatherization procedures led to an increase in indoor radon levels, as well as a warmer and less humid indoor environment. However, it did not affect indoor particulate mass concentration or indoor airborne bacteria load, and did only marginally affect the microbiome composition of residential homes. Finally, we found that changes in airborne bacterial load are more sensitive to shifts in season, whereas radon levels are more sensitive to ventilation rate.

microbiology↗

bioRxiv2020

Suppressing peatland methane production by electron snorkeling through pyrogenic carbon

Northern peatlands are experiencing more frequent fire events as a result of changing climate conditions. Forest fires naturally result in a direct and negative climate impact by emitting large amounts of carbon into the atmosphere. Recent studies show that this extensive emission may shift the soil carbon regime from a sink to a source. However, the fires also convert parts of the burnt biomass into pyrogenic carbon. Here, we show an indirect, but positive, climate impact induced by fire-derived pyrogenic carbon. We found that the accumulation of pyrogenic carbon reduced post-fire methane production from peatland soils by 13-24%. The conductive, capacitive, and redox-cycling electron transfer mechanisms enabled pyrogenic carbon to function as an electron snorkel, which redirected soil electron fluxes to facilitate alternative microbial respiration and reduced the rate of methane production by 50%. Given the fact that methane has a 34-fold greater warming potential than carbon dioxide, we estimate that global greenhouse gas emissions are reduced by 35 Tg CO2e annually through the electron snorkeling of pyrogenic carbon in peatlands. Our results highlight an important, but overlooked, function of pyrogenic carbon in neutralizing forest fire emissions and call for its consideration in the global carbon budget estimation.

microbiology↗

bioRxiv2019

An open-source multiple-bioreactor system for replicable gas-fermentation experiments: Nitrate feed results in stochastic inhibition events, but improves ethanol production of Clostridium ljungdahlii with CO2 and H2

The pH-value in fermentation broth has a large impact on the metabolic flux and growth behavior of acetogens. A decreasing pH level throughout time due to undissociated acetic acid accumulation is anticipated under uncontrolled pH conditions such as in bottle experiment. As a result, the impact of changes in the metabolism (e.g., due to a genetic modification) might remain unclear or even unrevealed. In contrast, pH-controlled conditions can be easily achieved in commercially available bioreactors. However, their acquisition is costly and their operation is time consuming, and therefore the experiment is often limited to a single bioreactor run. Here, we present a self-built, relatively cheap, and easy to handle open-source multiple-bioreactor system (MBS) consisting of six pH-controlled bioreactors at a 1-L scale. The functionality of the MBS was tested in three experiments by cultivating the acetogen Clostridium ljungdahlii with CO2 and H2 at steady-state conditions (=chemostat). The experiments were addressing the questions: (1) does the MBS provide replicable data for gas-fermentation experiments?; (2) does feeding acetate alter the production rate of ethanol; and (3) does feeding nitrate influence the product spectrum under controlled pH conditions with CO2 and H2? We applied four different periods in each experiment ranging from pH 6.0 to pH 4.5. Our data show high reproducibility for gas-fermentation experiments with C. ljungdahlii, using the MBS. We found that feeding acetate did not improve ethanol production, but rather impaired growth and reduced acetate production. Using nitrate as sole N-source, on the other hand, enhanced biomass production even at a low pH. However, we observed differences in growth, acetate, and ethanol production rates between triplicate bioreactors (n=3). We explained the different performances because of stochastic inhibition events, which we observed through the accumulation of nitrite, and which led to complete crashes at different operating times. One of these bioreactors recovered after the crash and showed enhanced ethanol production rates while simultaneously producing less acetate. The MBS offers a great opportunity to perform bench-scale bioreactor experiments at steady-state conditions with replicates, which is especially attractive for academia.

microbiology↗

bioRxiv2019

Syntrophy via interspecies H2 transfer between Christensenella and Methanobrevibacter underlies their global co-occurrence in the human gut

Across human populations, 16S rRNA gene-based surveys of gut microbiomes have revealed that the bacterial family Christensenellaceae and the archaeal family Methanobacteriaceae co-occur and are enriched in individuals with a lean, compared to an obese, BMI. Whether these association patterns reflect interactions between metabolic partners remains to be ascertained, as well as whether these associations play a role in the lean host phenotype with which they associate. Here, we validated previously reported co-occurrence patterns of the two families, and their association with a lean BMI, with a meta-analysis of 1,821 metagenomes derived from 10 independent studies. Furthermore, we report positive associations at the genus and species level between Christensenella spp. and Methanobrevibacter smithii, the most abundant methanogen of the human gut. By co-culturing three Christensenella spp. With M. smithii, we show that Christensenella spp. efficiently support the of M. smithii via H2 production, far better than Bacteroides thetaiotaomicron. C. minuta forms flocs colonized by M. smithii even when H2 is in excess. In culture with C. minuta, H2 consumption by M. smithii shifts the metabolic output of C. minutas fermentation towards acetate rather than butyrate. Together, these results indicate that the widespread co-occurrence of these microbiota is underpinned by both physical and metabolic interactions. Their combined metabolic activity may provide insights into their association with a lean host BMI. ImportanceThe human gut microbiome is made of trillions of microbial cells, most of which are Bacteria, with a subset of Archaea. The bacterial family Christensenellaceae and the archaeal family Methanobacteriaceae are widespread in human guts. They correlate with each other and with a lean body type. Whether species of these two families interact, and how they affect the body type, are unanswered questions. Here, we showed that species within these families correlate with each other across people. We also demonstrated that particular species of these two families grow together in dense flocs, wherein the bacteria provide hydrogen gas to the archaea, which then make methane. When the archaea are present, the ratio of bacterial products (which are nutrients for humans) is changed. These observations indicate when these species grow together, their products have the potential to affect the physiology of their human host.

microbiology↗