Rhizobium helanshanense sp. nov., a bacterium that nodulates Sphaerophysa salsula (Pall.) DC. in China

Abstract

Studying rhizobia in the root nodules of Sphaerophysa salsula (Pall.) DC in the northwest of China, we obtained five strains classified as genus Rhizobium on the basis of their 16S rRNA gene sequences. The sequence similarity of strain CCNWQTX14(T) with the most related species was 99.0%. Further phylogenetic analysis of housekeeping genes (recA and atpD) suggested the five strains comprised a novel lineage within Rhizobium. The nifH and nodD gene sequences of CCNWQTX14(T) were phylogenetically closely related with those of Sinorhizobium kummerowiae and R. sphaerophysae, respectively. The five strains isolated from different places were also distinct from related Rhizobium species using ERIC fingerprint profiles. The DNA-DNA hybridization value was 41.8% between CCNWQTX14(T) and Rhizobium sphaerophysae CCNWGS0238(T). Our novel strains were only able to form effective nodules on its original host Sphaerophysa salsula. Our data showed that the five Rhizobium strains formed a unique genomic species, for which a novel species Rhizobium helanshanense sp. nov. is proposed. The type strain is CCNWQTX14(T) (=ACCC 16237(T) =HAMBI 3083(T)).

Dynamics of bacterial and archaeal communities during horse bedding and green waste composting

“…Further reductions in thermophilic archaea and bacteria occurred between Aged phase and mature Compost, including M. thermoacetophila , T. terrifontis , R. profundi and R. marinus as well as the transient Ignavibacterium album and the extremophile and nematode pathogen Leucobacter chromiireducens ( Muir & Tan, 2008 ). Within highly diverse mature compost, large increases were observed in specialized species such as the obligate methanotroph Methylosarcina lacus and the nitrite-oxidizing bacteria Nitrospira japonica ( Fujitani et al, 2020 ; Kalyuzhnaya et al, 2005 ), but the community was best characterized by increases in 51 ESVs annotated as taxa within the order Rhizobiales which increased when compared to Aged phase, such as the methanotroph Methylocystis rosea , the nodule associated Mesorhizobium tamadayense and Rhizobium helanshanense , suggestive of a compost community which could benefit soil health and plant rhizosphere associations ( Qin et al, 2012 ; Rahalkar et al, 2018 ; Ramírez-Bahena et al, 2012 ).…”

“…Similarly, in addition to the more general evidence that compost application can help to suppress crop pathogens ( Bonanomi et al, 2007 ; Bonilla et al, 2012 ; Hoitink & Fahy, 1986 ; Termorshuizen et al, 2006 ), some species detected in the mature Compost are considered to be plant growth-promoting bacteria. These include A. ferrariae, Geobacter thiogenes, Geobacillus thermodenitrificans , Geobacillus stearothermophilus, L. chromiireducens, M. tamadayenses, P. aeruginosa , Paenibacillus yonginensis and R. helanshanense, which have been shown to bestow improved crop nutrient acquisition and/or resistance to different abiotic stresses such as drought, salinity, hydrocarbons, heavy metals and herbicides ( Aguiar et al, 2020 ; Marchant & Banat, 2010 ; Morais et al, 2004 ; Nevin et al, 2007 ; Pieterse et al, 2014 ; Qin et al, 2012 ; Rahalkar et al, 2018 ; Ramírez-Bahena et al, 2012 ; Sukweenadhi et al, 2014 ). Although species-level resolved profiling of complex microbial communities is challenging, identification and tracking of these potentially beneficial species to crops could inform our understanding of how compost could improve agricultural soils or the environmental impact of agriculture, in addition to the nutrient and soil stability properties traditionally associated with compost application.…”