Autochthonous carbon loading of macroalgae stimulates benthic biological nitrogen fixation rates in shallow coastal marine sediments.

Macroalgae, commonly known as seaweed, are foundational species in coastal ecosystems and contribute significantly to coastal primary production globally. However, the impact of macroalgal decomposition on benthic biological nitrogen fixation (BNF) after deposition to the seafloor remains largely unexplored. In this study, we measure BNF rates at three different sites at the Big Fisherman's Cove on Santa Catalina Island, CA, USA, which is representative of globally distributed rocky bottom macroalgal habitats.

Insights into the physiological and genomic characterization of three bacterial isolates from a highly alkaline, terrestrial serpentinizing system.

The terrestrial serpentinite-hosted ecosystem known as "The Cedars" is home to a diverse microbial community persisting under highly alkaline (pH ~ 12) and reducing (Eh < -550 mV) conditions. This extreme environment presents particular difficulties for microbial life, and efforts to isolate microorganisms from The Cedars over the past decade have remained challenging. Herein, we report the initial physiological assessment and/or full genomic characterization of three isolates: sp.

Magnetotactic bacteria: concepts, conundrums, and insights from a novel in situ approach using digital holographic microscopy (DHM).

Magnetotactic bacteria (MTB) are a diverse group of highly motile Gram-negative microorganisms with the common ability to orient along magnetic field lines, a behavior known as magnetotaxis. Ubiquitous in aquatic sediment environments, MTB are often microaerophilic and abundant at the oxic/anoxic interface. Magnetic field sensing is accomplished using intracellular, membrane-encased, iron-containing minerals known as magnetosomes.

gen. nov., sp. nov., sp. nov. and sp. nov., hyperalkaliphilic and facultative autotrophic bacteria isolated from terrestrial serpentinizing springs.

Three highly alkaliphilic bacterial strains designated as A1, H1 and B1 were isolated from two highly alkaline springs at The Cedars, a terrestrial serpentinizing site. Cells from all strains were motile, Gram-negative and rod-shaped. Strains A1, H1 and B1 were mesophilic (optimum, 30 °C), highly alkaliphilic (optimum, pH 11) and facultatively autotrophic.

Differences in Applied Redox Potential on Cathodes Enrich for Diverse Electrochemically Active Microbial Isolates From a Marine Sediment.

The diversity of microbially mediated redox processes that occur in marine sediments is likely underestimated, especially with respect to the metabolisms that involve solid substrate electron donors or acceptors. Though electrochemical studies that utilize poised potential electrodes as a surrogate for solid substrate or mineral interactions have shed some much needed light on these areas, these studies have traditionally been limited to one redox potential or metabolic condition. This work seeks to uncover the diversity of microbes capable of accepting cathodic electrons from a marine sediment utilizing a range of redox potentials, by coupling electrochemical enrichment approaches to microbial cultivation and isolation techniques.

Thioclava electrotropha sp. nov., a versatile electrode and sulfur-oxidizing bacterium from marine sediments.

A taxonomic and physiologic characterization was carried out on Thioclava strain ElOx9, which was isolated from a bacterial consortium enriched on electrodes poised at electron donating potentials. The isolate is Gram-negative, catalase-positive and oxidase-positive; the cells are motile short rods. The bacterium is facultatively anaerobic with the ability to utilize nitrate as an electron acceptor.

Quantifying Microorganisms at Low Concentrations Using Digital Holographic Microscopy (DHM).

Accurately detecting and counting sparse bacterial samples has many applications in the food, beverage, and pharmaceutical processing industries, in medical diagnostics, and for life detection by robotic missions to other planets and moons of the solar system. Currently, sparse bacterial samples are counted by culture plating or epifluorescence microscopy. Culture plates require long incubation times (days to weeks), and epifluorescence microscopy requires extensive staining and concentration of the sample.