The Evolutionary Kaleidoscope of Rhodopsins

Rhodopsins are widely distributed across all domains of life where they perform a plethora of functions through the conversion of electromagnetic radiation into physicochemical signals. As a result of an extensive survey of available genomic and metagenomic sequencing data, we reported the existence of novel clades and exotic sequence motifs scattered throughout the evolutionary radiations of both Type-1 and Type-3 rhodopsins that will likely enlarge the optogenetics toolbox. We expanded the typical rhodopsin blueprint by showing that a highly conserved and functionally important arginine residue (i.e., Arg82) was substituted multiple times during evolution by an extensive amino acid spectrum. We proposed the umbrella term Alt-rhodopsins (AltRs) for all such proteins that departed Arg82 orthodoxy. Some AltRs formed novel clades in the rhodopsin phylogeny and were found in giant viruses. Some newly uncovered AltRs were phylogenetically close to heliorhodopsins, which allowed a closer examination of the phylogenetic border between Type-1 rhodopsins and heliorhodopsins. Comprehensive phylogenetic trees and ancestral sequence reconstructions allowed us to advance the hypothesis that proto-heliorhodopsins were a eukaryotic innovation before their subsequent diversification into the extant Type-3 rhodopsins. IMPORTANCE The rhodopsin scaffold is remarkably versatile and widespread, coupling light availability to energy production and other light-dependent cellular responses with minor alterations to critical residues. We described an unprecedented spectrum of substitutions at one of the most conserved amino acids in the rhodopsin fold, Arg82. We denoted such phylogenetically diverse rhodopsins with the umbrella name Alt-rhodopsins (AltR) and described a distinct branch of AltRs in giant viruses. Intriguingly, some AltRs were the closest phylogenetic neighbors to Heliorhodopsins (HeRs) whose origins have remained enigmatic. Our analyses of HeR origins in the light of AltRs led us to posit a most unusual evolutionary trajectory that suggested a eukaryotic origin for HeRs before their diversification in prokaryotes

Complete Genome Sequence of an Uncultivated Freshwater Bacteroidota Lineage

We report here a complete metagenome-assembled genome belonging to the AKYH767 order within the Bacteroidota phylum. The recovered genome stems from a nonaxenic Amoebozoa culture from Lake Zürich and was assembled as a circular element at a length of 4.1 Mbp and a coverage of 115×

Complete Genome Sequence of an Uncultivated Freshwater Flavobacterium sp. Strain

Here, we report the complete metagenome-assembled genome of an uncultivated freshwater Flavobacterium sp. recovered from a nonaxenic Amoebozoa sp. culture. The chromosome was obtained from a metagenomic long-read sequencing run and was assembled as a circular element at a 51� coverage, length of 3.8 Mbp and a G1C content of 37.37%

Complete Genome Sequence from an Uncultivated Freshwater Elusimicrobiota Lineage

Here, we report the first complete genome of an uncultivated freshwater Elusimicrobiota organism recovered from a nonaxenic Amoebozoa sp. culture. The chromosome was obtained from a metagenomic long-read sequencing run and was assembled as a circular element at a 47× coverage, a length of 3.8 Mbp, and a G+C content of 68.6%

Study of Complete Genome Sequence of Uncultivated Hyphomonadaceae sp.

We report here a complete metagenome-assembled genome sequence belonging to the Proteobacteria phylum within the Hyphomonadaceae family. The circular chromosome was obtained from a metagenomic long-read sequencing run and displays a length of 4.1 Mbp along with a GC content of 62.5% at a coverage of 81×

New Halonotius Species Provide Genomics-Based Insights Into Cobalamin Synthesis in Haloarchaea

Hypersaline aquatic and terrestrial ecosystems display a cosmopolitan distribution. These environments teem with microbes and harbor a plethora of prokaryotic lineages that evaded ecological characterization due to the prior inability to cultivate them or to access their genomic information. In order to close the current knowledge gap, we performed two sampling and isolation campaigns in the saline soils of the Odiel Saltmarshes and the salterns of Isla Cristina (Huelva, Spain). From the isolated haloarchaeal strains subjected to high-throughput phylogenetic screening, two were chosen (F15BT and F9-27T) for physiological and genomic characterization due of their relatedness to the genus Halonotius. Comparative genomic analyses were carried out between the isolated strains and the genomes of previously described species Halonotius pteroides CECT 7525T, Halonotius aquaticus F13-13T and environmentaly recovered metagenome-assembled representatives of the genus Halonotius. The topology of the phylogenomic tree showed agreement with the phylogenetic ones based on 16S rRNA and rpoB′ genes, and together with average amino acid and nucleotide identities suggested the two strains as novel species within the genus. We propose the names Halonotius terrestris sp. nov. (type strain F15BT = CECT 9688T = CCM 8954T) and Halonotius roseus sp. nov. (type strain F9-27T = CECT 9745T = CCM 8956T) for these strains. Comparative genomic analyses within the genus highlighted a typical salt-in signature, characterized by acidic proteomes with low isoelectric points, and indicated heterotrophic aerobic lifestyles. Genome-scale metabolic reconstructions revealed that the newly proposed species encode all the necessary enzymatic reactions involved in cobalamin (vitamin B12) biosynthesis. Based on the worldwide distribution of the genus and its abundance in hypersaline habitats we postulate that its members perform a critical function by being able to provide “expensive” commodities (i.e., vitamin B12) to the halophilic microbial communities at large.España , MINECO Project CGL2017-83385-PEspaña, Junta de Andalucía BIO213España, Ministerio de Educación, Cultura y Deporte FEMS-GO-2018-139España FEDER FPU14/0512

Complete genome of Flavobacterium pectinovorum str. ZE23VCel01 obtained through Nanopore Q20+ chemistry

This study reports the complete genome of Flavobacterium pectinovorum str. ZE23VCel01 isolated from a freshwater environment. By means of Nanopore Q20+ chemistry, the chromosome was assembled as a circular element with a length of 5.9 Mbp, a GC content of 33.58%, and a coverage of 122×

Pseudomonas kielensis str. Ze23jcel16 complete genome obtained through R10.4.1 Nanopore Flow cell chemistry

Here, we report the complete genome of Pseudomonas kielensis str. Ze23jcel16 isolated from a freshwater sample. The high-quality chromosome was obtained employing R10.4.1 Nanopore Flow cell chemistry and was assembled as a circular element at 45× coverage, a length of 5.8 Mbp, and a G+C content of 61.15%

Q20+ Nanopore sequencing data recover a high-quality Asticcacaulis sp. genome

We present here the complete genome of Asticcacaulis sp. ZE23SCel15. The strain was isolated from the surface water of Lake Zurich, Switzerland. The assembly of high-quality Q20+ Nanopore data yielded a circular genome with ~3.8 Mb (coverage: 34×) and a GC content of 56.81%

A novel Methylomirabilota methanotroph potentially couples methane oxidation to iodate reduction

Impact statement Methane oxidizing microbes play a key role in reducing the emission of this potent greenhouse gas to the atmosphere. The known versatility of the recently discovered anaerobic Methylomirabilota methanotrophs is limited. Here, we report a novel uncultured Methylomirabilis species, Candidatus Methylomirabilis iodofontis, with the genetic potential of iodate respiration from biofilm in iodine‐rich cavern spring water. Star‐like cells resembling Methylomirabilis oxyfera were directly observed from the biofilm and a high‐quality metagenome‐assembled genome (MAG) of Ca. M. iodofontis was assembled. In addition to oxygenic denitrification and aerobic methane oxidation pathways, the M. iodofontis MAG also indicated its iodatereducing potential, a capability that would enable the bacterium to use iodate other than nitrite as an electron acceptor, a hitherto unrecognized metabolic potential of Methylomirabilota methanotrophs. The results advance the current understanding of the ecophysiology of anaerobic Methylomirabilota methanotrophs and may suggest an additional methane sink, especially in iodate‐rich ecosystems