Biology subjects

McKaig, J. M.

Publications and source records attributed to McKaig, J. M..

3 recordsLinked to original sources

bioRxiv2026

Anaerobic methane oxidation by ANME-2a at two molar chloride in Orca Basin

Anaerobic methane oxidation, typically mediated by consortia of archaea and bacteria, is a key process in the global methane cycle, but little is known about its upper salinity limits. We characterized the microbial methane cycle in the anoxic, hypersaline Orca Basin using metagenomics, metatranscriptomics, fluorescence in situ hybridization, and geochemical measurements at sub-meter resolution. In the brine, we detected transcriptional activity of the halophilic methylotrophic methanogen Methanohalophilus, consistent with a biological source for Orca Basin methane. In the particle-rich halocline ([~]2 M Cl-; [~]2235 meters depth), high mcrA transcription by a novel ANME-2a species was co-located with a positive shift in {delta}13C-CH4 indicative of anaerobic oxidation of methane. ANME-2a also transcribed genes for biosynthesis of the osmolyte N({varepsilon})-acetyl-{beta}-L-lysine, supporting adaptation for hypersaline conditions. At the same depth, consortia of sarcina-like archaea, likely ANME-2a, were observed in association with vibrioid and filamentous bacteria, potentially members of a halotolerant genus in the order Desulfobulbales (family SURF-16, which includes the previously identified ANME partner Seep-DBB) that were active at the same depth. At and above the oxic-anoxic interface, aerobic methane oxidation appears to be mediated by three genera of uncultivated Methylococcales bacteria. Our results double the upper salinity range of ANME-2a to [~]2 M Cl- and reveal the key microbial players in the methane bio-filter between the Orca Basin brine and overlying seawater.

microbiology↗

bioRxiv2025

Validation of Gentamicin and Streptomycin Stability for On-Orbit Microbial Monitoring

The Genomic Enumeration of Antibiotic Resistance in Space (GEARS) flight project seeks to characterize the frequency and genomic identity of antibiotic-resistant organisms on the ISS and expand in-space sequencing-based diagnostic capabilities. This project selects for antibiotic-resistant microbes on space station surfaces using agar plates containing antibiotics, which can require storage of these plates for several months. However, little published data is available on the longevity of antibiotics in agar plates. Here, we describe the process of antibiotic selection and validation of antibiotic stability for GEARS. A literature review was conducted on several antibiotics for their intrinsic and acquired resistance in Enterococcus and Staphylococcus and stability in solution and in agar. Gentamicin and streptomycin were selected for a long-term study tracking changes in bactericidal ability of the antibiotics in agar plates. After 6.5 months of storage at 4{degrees}C, we found that both antibiotic types remained stable throughout the test period, although they both exhibited evidence of slight degradation. These findings indicated that either antibiotic would be sufficient for the GEARS study based on stability under cold stowage conditions. Furthermore, this study generated information on long-term stability of antibiotics in agar, which can be useful for microbiology applications beyond spaceflight studies.

microbiology↗

bioRxiv2023

Translation as a Biosignature

Life on Earth relies on mechanisms to store heritable information and translate this information into cellular machinery required for biological activity. In all known life, storage, regulation, and translation are provided by DNA, RNA, and ribosomes. Life beyond Earth, even if ancestrally or chemically distinct from life as we know it may utilize similar structures: it has been proposed that charged linear polymers analogous to nucleic acids may be responsible for storage and regulation of genetic information in non-terran biochemical systems. We further propose that a ribosome-like structure may also exist in such a system, due to the evolutionary advantages of separating heritability from cellular machinery. Here, we use a solid-state nanopore to detect DNA, RNA, and ribosomes, and demonstrate that machine learning can distinguish between biomolecule samples and accurately classify new data. This work is intended to serve as a proof of principal that such biosignatures (i.e., informational polymers or translation apparatuses) could be detected, for example, as part of future missions targeting extant life on Ocean Worlds. A negative detection does not imply the absence of life; however, detection of ribosome-like structures could provide a robust and sensitive method to seek extant life in combination with other methods. One Sentence SummaryLife, defined as a chemical system capable of Darwinian evolution, likely requires an apparatus to translate heritable instructions into cellular machinery, and we propose to detect this as a biosignature of extant life beyond Earth.

biophysics↗