Abstract
Abstract
Four rhizobial strains isolated from root nodules of tropical leguminous plants in Costa Rica were characterized. Strain LEGMi-135b was isolated from
Lonchocarpus felipei
root nodules, LEGMi-12c from
Cojoba arborea
, LEGMi-198b from
Calliandra haematocephala
and
Rhizobium altiplani
LEGMi-166a from
Mimosa pigra
. Phylogenetic analyses based on the 16S rRNA gene and four concatenated housekeeping genes (
recA, atpD, GATase
and
gyrB
) placed these strains within the genera
Martinezella
(LEGMi-12c, LEGMi-135b, and LEGMi-198b) and
Rhizobium
(LEGMi-166a). Genome-based analyses showed that strain LEGMi-135b exhibited an average nucleotide identity (ANI) value of 94% and a digital DNA-DNA hybridization (dDDH) value of 53.2% compared with its closest related species,
Martinezella hainanensis
CCBAU 57015
T
, supporting its classification as a distinct species. LEGMI-12c exhibited ANI and dDDH values of 98% and 87%, respectively, compared with
Martinezella hainanensis
CCBAU 57015
T
. LEGMi-198b showed the highest similarity to
Rhizobium cerradonense
CNPSo 3464, with ANI and dDDH values of 98% and 81.4%, respectively; however, this taxon has not been validly published. LEGMi-166a exhibited ANI and dDDH values of 100% and 99.3%, respectively, compared with
Rhizobium altiplani
BR 10423ᵀ, confirming its assignment to this species. Additionally, differentiation of strains LEGMi-135b and LEGMi-198b from their closest phylogenetic relatives was supported by phenotypic, physiological, and biochemical analyses. Based on the combined genomic, phenotypic, and biochemical evidence, we propose the establishment of the novel rhizobial species
Martinezella legmii
sp. nov., with strain LEGMi-135b designated as the type strain (LEGMi-135bᵀ), and
Martinezella ivanii
sp. nov., with strain LEGMi-198b designated as the type strain (LEGMi-198bᵀ). This study expands our understanding of rhizobial diversity associated with nitrogen-fixing symbioses, particularly among tropical leguminous plants from Costa Rica.
Data summary
The raw reads of the three
Martinezella
spp. and one
Rhizobium
sp. isolates have been deposited in GenBank under BioProject PRJNA1084876 and SRA accession SRP493729. The corresponding BioSample and genome accessions are:
Martinezella
sp. LEGMi-12c (SAMN44800730; GCF_054114145.1), LEGMi-135b (SAMN44800728; GCF_054114165.1),
Rhizobium
sp. LEGMi-166a (SAMN46966679; GCF_054114185.1), and
Martinezella
sp. LEGMi-198b (SAMN44800729; GCF_054114205.1). The 16S rRNA sequences are available under accessions
PP439182
,
PP439210
,
PP439229
, and
PP439245
, respectively.