Paraburkholderia strydomiana sp. nov. and Paraburkholderia steynii sp. nov.: rhizobial symbionts of the fynbos legume Hypocalyptus sophoroides

Abstract

Twelve nodulating Paraburkholderia strains isolated from indigenous South African fynbos legume Hypocalyptus sophoroides were investigated to determine their taxonomic status.Genealogical concordance analysis, based on six loci (16S rRNA, atpD, recA, rpoB, lepA and gltB), revealed that they separate into two consistent and exclusive groups. Average nucleotide identity and DNA-DNA hybridisation comparisons indicated that they were sufficiently divergent from their closest known phylogenetic relatives (Paraburkholderia caledonica and Paraburkholderia terrae, respectively) to be regarded as novel species. This was also supported by the results of fatty acid analysis and metabolic characterisation. For these two isolate groups, we accordingly propose the new species Paraburkholderia strydomiana sp. nov. with WK1.1f T (= LMG 28731 T = SARCC1213 T ) as its type strain and Paraburkholderia steynii sp. nov. with HC1.1ba T (= LMG 28730 T = SARCC696 T ) as its type strain. Our data thus showed that H. sophoroides may be considered a promiscuous symbiotic partner due to its ability to associate with multiple species of Paraburkholderia.

The history and distribution of nodulating Paraburkholderia, a potential inoculum for Fynbos forage species

“…Most of the rhizobial species occurring in the CCR can establish nitrogen‐fixing symbioses with multiple papilionoid species (Table 2). Future exploration of the legume–rhizobium symbiosis in the region will likely show that this is also true for bacteria that have been reported from single host species (e.g., P. steynii and P. strydomiana that nodulate Hypocalyptus sophoroides and P. rhynchosiae that nodulates Rhynchosia ferulifolia ) (Beukes, Steenkamp, et al., 2019; De Meyer, Cnockaert, Ardley, Trengove, et al., 2013; Table 2). Likewise, many CCR papilionoids are promiscuous in terms of nodulating partner as several species are capable of nodulating with multiple Paraburkholderia species.…”

“…Of the 20 known rhizobial Paraburkholderia species, eight were found in the CCR. These include the first beta‐rhizobial species to be recognized, P. tuberum (Moulin et al., 2001; Vandamme et al., 2002) as well as P. kirstenboschensis , P. strydomiana , P. steynii , P. dilworthii , P. sprentiae , P. dipogonis and P. rhynchosiae (Beukes, Steenkamp, et al., 2019; De Meyer, Cnockaert, Ardley, Maker, et al., 2013; De Meyer, Cnockaert, Ardley, Trengove, et al., 2013; De Meyer et al., 2014; Sheu et al., 2015; Steenkamp et al., 2015).…”

“…Likewise, many CCR papilionoids are promiscuous in terms of nodulating partner as several species are capable of nodulating with multiple Paraburkholderia species. For example, Hypocalyptus sophoroides can form nodules in association with at least five Paraburkholderia species (i.e., P. dipogonis , P. kirstenboschensis , P. steynii , P. strydomiana and P. tuberum ) (Beukes, Steenkamp, et al., 2019; Lemaire, Chimphango, et al., 2016; Sheu et al., 2015; Steenkamp et al., 2015; Table 2), while Virgilia oroboides nodulates with P. dipogonis , P. kirstenboschensis , P. tuberum and P. phymatum (Lemaire, Chimphango, et al., 2016; Sheu et al., 2015; Steenkamp et al., 2015; Table 2). Although some papilionoids have been reported to associate with one or only a few rhizobial species, this is likely due to limited sampling intensity.…”

Microbial Communities in the Fynbos Region of South Africa: What Happens during Woody Alien Plant Invasions

“…It has been suggested that bacterial groups evolved in this biome to be hyper-diverse and in many cases some species are only found in this part of the world as was the case with Burkholderia [91,92] and Paraburkholderia [93]. This group of bacteria functions as symbionts of plants to acquire nitrogen through fixation [94].…”

“…appears to have nodulation genes that are closely related and only form nodules in the presences of fynbos papilionoid legumes [95]. Numerous studies isolated and characterised species from this bacterial group, including some novel strains [91,93,96]. Most of the strains isolated from fynbos plants are shown to be highly adapted to low pH environments, consistent with the fynbos soils [97].…”