A bacterial strain designated GR21 T was isolated from apoplastic fluid of Saccharum officinarum (sugar cane). Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate forms a separate branch within the family 'Paenibacillaceae', with Paenibacillus as the closest related genus. Within this genus, the closest related species is Paenibacillus xylanilyticus, with 93.4 % similarity to the sequence of the type strain. The isolate has Gram-variable, facultatively anaerobic, rod-shaped cells, motile by polar and subpolar flagella. Round, non-ornamented, central or subterminal spores are formed in unswollen sporangia. The strain is catalase-positive and oxidase-negative on nutrient agar medium. Cellulose and aesculin were hydrolysed, whereas xylan, starch and gelatin were not. Growth was supported by many carbohydrates as carbon sources. Strain GR21 T displayed a lipid profile consisting of diphosphatidylglycerol, phosphatidylglycerol, an unknown aminophospholipid, two unknown glycolipids and an unknown phosphoglycolipid. MK-7 was the predominant menaquinone and anteiso-C 15 : 0 was the major fatty acid. The DNA G+C content was 57.8 mol%. Phylogenetic and phenotypic analyses, including assimilation of carbon sources and exoenzyme production commonly used for classification within the family 'Paenibacillaceae', showed that strain GR21 T belongs to a new genus within this family, for which the name Saccharibacillus sacchari gen. nov., sp. nov. is proposed. The type strain of Saccharibacillus sacchari is GR21 T (5LMG 24085 T 5DSM 19268 T ).The family 'Paenibacillaceae' currently contains eight genera of Gram-positive, -variable or -negative sporulating bacilli. The description of the most recently described genus of the family, Cohnella (Kämpfer et al., 2006), was based on its phylogenetic relationship with respect to the remaining genera of the family as well as on its polar lipid profile. Some species of this family, mainly belonging to the genus Paenibacillus, have been isolated from the plant rhizosphere, but only Paenibacillus polymyxa has been reported as a plant endophyte (Cho et al., 2006). In the present work, we describe the isolation and identification of a novel bacterium isolated from apoplastic sap of sugar cane (Saccharum officinarum) in Granada (Spain).For the isolation of strain GR21 T , stem pieces were washed with sterile tap water and soaked in 5 % chloramine T solution for 2 min. After removal of the rind with a sterile sharp knife, the cylinder of parenchyma tissue was rinsed with 70 % ethanol and flame-sterilized. Apoplastic sap from the internodes was collected by centrifugation according to Dong et al. (1994), and serial dilutions were streaked on tryptone soybean agar (TSA) and incubated at 30 u C for 7-10 days. After flaming, no contamination was observed when several stem pieces were incubated on TSA plates.Strain GR21 T was grown on nutrient agar for 48 h at 22 u C to check for motility by phase-contrast microscopy using the hanging drop method. Gram staining was carried o...