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A novel methanogenic strain, CaP3V-MF-L2AT, was isolated from an exploratory oil well from Cahuita National Park, Costa Rica. The cells were irregular cocci, 0.8–1.8 μm in diameter, stained Gram-negative and were motile. The strain utilized H2/CO2, formate and the primary and secondary alcohols 1-propanol and 2-propanol for methanogenesis, but not acetate, methanol, ethanol, 1-butanol or 2-butanol. Acetate was required as carbon source. The novel isolate grew at 25–40 °C, pH 6.0–7.5 and 0–2.5% (w/v) NaCl. 16S rRNA gene sequence analysis revealed that the strain is affiliated to the genus Methanofollis. It shows 98.8% sequence similarity to its closest relative Methanofollis ethanolicus. The G + C content is 60.1 mol%. Based on the data presented here type strain CaP3V-MF-L2AT (= DSM 113321T = JCM 39176T) represents a novel species, Methanofollis propanolicus sp. nov.

The lack of a nucleus is the defining cellular feature of bacteria and archaea. Consequently, transcription and translation are occurring in the same compartment, proceed simultaneously and likely in a coupled fashion. Recent cryo-electron microscopy (cryo-EM) and tomography data, also combined with crosslinking-mass spectrometry experiments, have uncovered detailed structural features of the coupling between a transcribing bacterial RNA polymerase (RNAP) and the trailing translating ribosome in Escherichia coli and Mycoplasma pneumoniae. Formation of this supercomplex, called expressome, is mediated by physical interactions between the RNAP-bound transcription elongation factors NusG and/or NusA and the ribosomal proteins including uS10. Based on the structural conservation of the RNAP core enzyme, the ribosome, and the universally conserved elongation factors Spt5 (NusG) and NusA, we discuss requirements and functional implications of transcription-translation coupling in archaea. We furthermore consider additional RNA-mediated and co-transcriptional processes that potentially influence expressome formation in archaea.

The prokaryotic transcriptome is shaped by transcriptional and posttranscriptional events that define the characteristics of an RNA, including transcript boundaries, the base modification status, and processing pathways to yield mature RNAs. Currently, a combination of several specialised short-read sequencing approaches and additional biochemical experiments are required to describe all transcriptomic features. In this study, we present native RNA sequencing of bacterial ( E. coli ) and archaeal ( H. volcanii, P. furiosus ) transcriptomes employing the Oxford Nanopore sequencing technology. Based on this approach, we could address multiple transcriptomic characteristics simultaneously with single-molecule resolution. Taking advantage of long RNA reads provided by the Nanopore platform, we could accurately (re-)annotate large transcriptional units and boundaries. Our analysis of transcription termination sites revealed that diverse termination mechanisms are in place in archaea. Moreover, we shed light on the poorly understood rRNA processing pathway in archaea and detected new processing intermediates. One of the key features of native RNA sequencing is that RNA modifications are retained. We could confirm this ability by analysing the well-known KsgA-dependent rRNA methylation sites. Notably, our analysis suggests that rRNA modifications are more abundant in a hyperthermophilic organism.