Cultured deep-sea PVC bacteria shed light on eukaryogenesis

Abstract

Evolutionary relationship between prokaryotes and eukaryotes continues to fascinate biologists. Accumulated studies suggest a eukaryogenesis model based on the PVC (Planctomycetes-Verrucomicrobia-Chlamydiae) bacteria. However, a decisive PVC-based eukaryogenesis scenario has not yet been reported. Here, we isolated PVC bacteria, unique for dividing by budding and for possessing developed endomembrane systems, from the deep sea. In cultured PVC bacterial strains, we detected typical eukaryotic organelle-like structures including endoplasmic reticulum, Golgi apparatus, vesicles, vacuoles and actin/tubulin-based microfilaments. Strikingly, we observed a nucleolus-containing nucleus in a Verrucomicrobia strain, which divides by mitosis. Transcriptomic results further demonstrated abundant presence of genes associated with eukaryotic cellular processes including membrane fusion. We propose that the prominent capability of membrane fusion drives eukaryogenesis by enabling PVC bacteria to evolve eukaryotic cellular features.

Polysaccharides induce deep-seaLentisphaeraestrains to release chronic bacteriophages

“…These CAZymes (GH18 and GH127) were specifically responsible for degrading polysaccharides 68 . The energizer ExbB was an important part of the TonB-system, which was often present in Bacteroides and responsible for transport oligosaccharides from the outer membrane into the periplasm 69,70 , but they were absent in the genomes of strains WC36 and zth2. Therefore, these AMGs encoding TonB-system energizer ExbB and glycoside hydrolases could reprogram the polysaccharide metabolism of host cells (strains WC36 and zth2) by providing the supplemental support to key metabolisms.…”