Complex history of aerobic respiration and phototrophy in the Chloroflexota class Anaerolineae revealed by high-quality draft genome ofCa. Roseilinea mizusawaensis AA3_104

Abstract

The candidate genus Roseilinea is a novel lineage in the Chloroflexota (formerly Chloroflexi or green nonsulfur bacteria) phylum known so far only from very incomplete metagenome-assembled genomes and preliminary enrichments. Roseilinea is notable for appearing capable of anoxygenic photoheterotrophy despite being only distantly related to well-known phototrophic Chloroflexota in the Chloroflexia class such as Chloroflexus and Roseiflexus. Here, we present a high quality metagenome-assembled genome of a member of Roseilinea, greatly improving our understanding of the metabolic capacity and taxonomic assignment of this genus. These data allow us to confidently describe the genetic basis for photoheterotrophy in these organisms as well as propose a candidate family for these organisms, Ca. Roseilineaceae, within the Anaerolineae class of Chloroflexota.

Atmospheric chemosynthesis is phylogenetically and geographically widespread and contributes significantly to carbon fixation throughout cold deserts

“…Photoautotrophic green sulfur bacteria belonging to the class Chlorobi were notably undetected in both the MAGs and metagenomes, as were photoheterotrophic taxa including the genera Candidatus Chloracidobacterium, Heliobacterium, and Gemmatimonas [36][37][38][39][40][41] . Chloro exia, the sole photoautotrophic class within Chloro exota 42 , was undetected. The only Chloro exota MAGs represented belonged to the chemoautotrophic order Thermomicrobiales (n=7), which is associated with CO oxidation 18,43 , and the poorly characterised candidate order 54-19 (n=2).…”

Temperature and Geographic Location Impact the Distribution and Diversity of Photoautotrophic Gene Variants in Alkaline Yellowstone Hot Springs

“…2B ). pufL and pufM encode PufL and PufM, membrane-spanning proteins that bind bacteriochlorophylls in type-II reaction centers, while pufC gene encodes a cytochrome involved in photosynthetic electron transfer ( 19 , 45 , 46 ). puf gene abundances ranged from rare (0.001 normalized reads mapped) to 1.5 normalized reads mapped ( Fig.…”

“…Chloroflexi are the most abundant and widespread anoxygenic phototroph in alkaline hot springs ( 4 , 5 , 10 , 11 , 16 , 17 ). Phototrophy (photoautotrophy, photomixotrophy, and photoheterotrophy) in phylum Chloroflexi is limited to class Chloroflexales with one exception, “Candidatus Roseilinea” ( 18 , 19 ). Unlike cyanobacteria that rely on the Calvin cycle for autotrophy, photoautotrophic Chloroflexi (meaning both photoautotrophs and photomixotrophs) genomes can vary in carbon assimilation genes: both Chloroflexus and Roseiflexus genomes contain genes for the autotrophic 3-hydroxypropionate bicycle (3-HPB) ( 20 , 21 ), but only Chloroflexus isolates have been grown in the absence of acetate ( 22 , 23 ).…”

Role of horizontal gene transfers and microbial ecology in the evolution of fluxes through the tricarboxylic acid cycle

“…An alternative plausible explanation for these findings is that during the CCS/CCL and ACL divergence, TCA was not cyclical in its modern form or that citrate cleavage reaction was involved in different ancient biochemical pathways. An additional complicating factor may have been the proposed horizontal transfer of aerobic respiration genes in some extant lineages (Kennedy et al, 2001;Ward et al, 2021). Patchy distribution of rTCA is due to HGTs, not multiple losses.…”