Biology subjects

Pearson, A.

Publications and source records attributed to Pearson, A..

3 recordsLinked to original sources

bioRxiv2019

Energy flux controls tetraether lipid cyclization in Sulfolobus acidocaldarius

Microorganisms regulate the composition of their membranes in response to environmental cues. Many archaea maintain the fluidity and permeability of their membranes by adjusting the number of cyclic moieties within the cores of their glycerol dibiphytanyl glycerol tetraether (GDGT) lipids. Cyclized GDGTs increase membrane packing and stability, which has been shown to help cells survive shifts in temperature and pH. However, the extent of this cyclization also varies with growth phase and electron acceptor or donor limitation. These observations indicate a relationship between energy metabolism and membrane composition. Here we show that the average degree of GDGT cyclization increases with doubling time in continuous cultures of the thermoacidophile Sulfolobus acidocaldarius (DSM 639). This is consistent with the behavior of a mesoneutrophile, Nitrosopumilus maritimus SCM1. Together, these results demonstrate that archaeal GDGT distributions can shift in response to electron donor flux and energy availability, independent of pH or temperature. Paleoenvironmental reconstructions based on GDGTs thus capture the energy available to microbes, which encompasses fluctuations in temperature and pH, as well as electron donor and acceptor availability. The ability of Archaea to adjust membrane composition and packing may be an important strategy that enables survival during episodes of energy stress.\n\nSignificance StatementMicrobial lipid membranes protect and isolate a cell from its environment while regulating the flow of energy and nutrients to metabolic reaction centers within. We demonstrate that membrane lipids change as a function of energy flux using a well-studied archaeon that thrives in acidic hot springs and observe an increase in membrane packing as energy becomes more limited. These observations are consistent with chemostat experiments utilizing a low temperature, neutral pH, marine archaeon. This strategy appears to regulate membrane homeostasis is common across GDGT-producing lineages, demonstrating that diverse taxa adjust membrane composition in response to chronic energy stress.

microbiology↗

bioRxiv2019

Illuminating microbial species-specific effects on organic matter remineralization in marine sediments

Marine microorganisms play a fundamental role in the global carbon cycle by mediating the sequestration of organic matter in ocean waters and sediments. A better understanding of how biological factors, such as microbial community composition, influence the lability and fate of organic matter is needed. Here, we explored the extent to which organic matter remineralization is influenced by species-specific metabolic capabilities. We carried out aerobic time-series incubations of Guaymas basin sediments to quantify the dynamics of carbon utilization by two different heterotrophic marine isolates. Continuous measurement of respiratory CO2 production and its carbon isotopic compositions (13C and 14C) shows species-specific differences in the rate, quantity, and type of organic matter remineralized. Each species was incubated with hydrothermally-influenced vs. unimpacted sediments, resulting in a ~3-fold difference in respiratory CO2 yield across the experiments. Genomic analysis indicated that the observed carbon utilization patterns may be attributed in part to the number of gene copies encoding for extracellular hydrolytic enzymes. Our results demonstrate that the lability and remineralization of organic matter in marine environments is not only a function of chemical composition and/or environmental conditions, but also a function of the microorganisms that are present and active.

microbiology↗

bioRxiv2019

Host engineering for improved valerolactam production in Pseudomonas putida

Pseudomonas putida is a promising bacterial chassis for metabolic engineering given its ability to metabolize a wide array of carbon sources, especially aromatic compounds derived from lignin. However, this omnivorous metabolism can also be a hindrance when it can naturally metabolize products produced from engineered pathways. Herein we show that P. putida is able to use valerolactam as a sole carbon source, as well as degrade caprolactam. Lactams represent important nylon precursors, and are produced in quantities exceeding one million tons per year[1]. To better understand this metabolism we use a combination of Random Barcode Transposon Sequencing (RB-TnSeq) and shotgun proteomics to identify the oplBA locus as the likely responsible amide hydrolase that initiates valerolactam catabolism. Deletion of the oplBA genes prevented P. putida from growing on valerolactam, prevented the degradation of valerolactam in rich media, and dramatically reduced caprolactam degradation under the same conditions. Deletion of oplBA, as well as pathways that compete for precursors L-lysine or 5-aminovalerate, increased the titer of valerolactam from undetectable after 48 hours of production to ~90 mg/L. This work may serve as a template to rapidly eliminate undesirable metabolism in non-model hosts in future metabolic engineering efforts.

synthetic biology↗