title: Rhizobium paknamense sp. nov., isolated from lesser duckweeds (Lemna aequinoctialis).
abstract: A Gram-stain-negative, rod-shaped bacterium was isolated and designated strain L6-8(T) during a study of endophytic bacterial communities in lesser duckweed (Lemna aequinoctialis). Cells of strain L6-8(T) were motile with peritrichous flagella. The analysis of the nearly complete 16S rRNA gene sequence indicated that strain L6-8(T) was phylogenetically related to species of the genus Rhizobium. Its closest relatives were Rhizobium borbori DN316(T) (97.6 %), Rhizobium oryzae Alt 505(T) (97.3 %) and Rhizobium pseudoryzae J3-A127(T) (97.0 %). The sequence similarity analysis of housekeeping genes recA, glnII, atpD and gyrB showed low levels of sequence similarity (<91.5 %) between strain L6-8(T) and other species of the genus Rhizobium with validly published names. The pH range for growth was 4.0-9.0 (optimum 6.0-7.0), and the temperature range for growth was 20-45 °C (optimum 30 °C). Strain L6-8(T) tolerated NaCl up to 2 % (w/v) (optimum 1 % NaCl). The predominant components of cellular fatty acids were C19 : 0 cyclo ω8c (31.32 %), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c; 25.39 %) and C16 : 0 (12.03 %). The DNA G+C content of strain L6-8(T) was 60.4 mol% (Tm). nodC and nifH were not amplified in strain L6-8(T). DNA-DNA relatedness between strain L6-8(T) and R. borbori DN316(T), R. oryzae Alt505(T) and R. pseudoryzae J3-A127(T) was between 11.2 and 18.3 %. Based on the sequence similarity analyses, phenotypic, biochemical and physiological characteristics and DNA-DNA hybridization, strain L6-8(T) could be readily distinguished from its closest relatives and represents a novel species of the genus Rhizobium, for which the name Rhizobium paknamense sp. nov. is proposed. The type strain is L6-8(T) ( = NBRC 109338(T) = BCC 55142(T)).
authors.affiliation: Actinobacterial Research Unit, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.|Department of Biology, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.
authors.forename: Chokchai
authors.initials: C
authors.lastname: Kittiwongwattana
authors.affiliation: Microbial Resource Management Unit, Scientific Instrument Center, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.|Actinobacterial Research Unit, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.|Department of Biology, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand.
authors.forename: Chitti
authors.initials: C
authors.lastname: Thawai
mesh_terms: D029064:Araceae / Q000382:microbiology*; D015373:Bacterial Typing Techniques; D001482:Base Composition; D004269:DNA, Bacterial / Q000235:genetics; D005227:Fatty Acids / Q000032:analysis; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012231:Rhizobium / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D013785:Thailand; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D005227:Fatty Acids; D012336:RNA, Ribosomal, 16S