NDLI: Genome-Scale Mutational Analysis of Cathode-Oxidizing Thioclava electrotropha ElOx9T

Content Provider	Directory of Open Access Journals (DOAJ)
Author	Joshua D. Sackett Nitin Kamble Edmund Leach Taruna Schuelke Elizabeth Wilbanks Annette R. Rowe
Abstract	Extracellular electron transfer (EET) – the process by which microorganisms transfer electrons across their membrane(s) to/from solid-phase materials – has implications for a wide range of biogeochemically important processes in marine environments. Though EET is thought to play an important role in the oxidation of inorganic minerals by lithotrophic organisms, the mechanisms involved in the oxidation of solid particles are poorly understood. To explore the genetic basis of oxidative EET, we utilized genomic analyses and transposon insertion mutagenesis screens (Tn-seq) in the metabolically flexible, lithotrophic Alphaproteobacterium Thioclava electrotropha ElOx9T. The finished genome of this strain is 4.3 MB, and consists of 4,139 predicted ORFs, 54 contain heme binding motifs, and 33 of those 54 are predicted to localize to the cell envelope or have unknown localizations. To begin to understand the genetic basis of oxidative EET in ElOx9T, we constructed a transposon mutant library in semi-rich media which was comprised of >91,000 individual mutants encompassing >69,000 unique TA dinucleotide insertion sites. The library was subjected to heterotrophic growth on minimal media with acetate and autotrophic oxidative EET conditions on indium tin oxide coated glass electrodes poised at –278 mV vs. SHE or un-poised in an open circuit condition. We identified 528 genes classified as essential under these growth conditions. With respect to electrochemical conditions, 25 genes were essential under oxidative EET conditions, and 29 genes were essential in both the open circuit control and oxidative EET conditions. Though many of the genes identified under electrochemical conditions are predicted to be localized in the cytoplasm and lack heme binding motifs and/or homology to known EET proteins, we identified several hypothetical proteins and poorly characterized oxidoreductases that implicate a novel mechanism(s) for EET that warrants further study. Our results provide a starting point to explore the genetic basis of novel oxidative EET in this marine sediment microbe.
e-ISSN	1664302X
DOI	10.3389/fmicb.2022.909824
Journal	Frontiers in Microbiology
Volume Number	13
Language	English
Publisher	Frontiers Media S.A.
Publisher Date	2022-06-01
Publisher Place	Switzerland
Access Restriction	Open
Subject Keyword	Microbiology Extracellular Electron Transfer (eet) Lithotrophy Tn-seq Marine Bacterium Marine Sediment Electrotroph
Content Type	Text
Resource Type	Article

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