A newly isolated strain B69 with broad antimicrobial activity was identified as Paenibacillus elgii by 16S rRNA gene sequence analysis, along with physiological and biochemical characterization. Two antimicrobial compounds, named as Pelgipeptins A and B, were isolated from the culture medium using MCI GEL CHP20P column chromatography and HPLC methods. The molecular masses of Pelgipeptins A and B were 1072 and 1100 Da, respectively. The ESI-CID-MS and amino acid analysis suggested that both of them belonged to the polypeptin family, and Pelgipeptin A was unequivocally characterized as a new antibiotic. These two antibiotics were active against all the tested bacterial strains and displayed strong antifungal activity against several soil-borne fungal pathogens, with minimal inhibitory concentration values of 6.25-50 mug mL(-1). Furthermore, stability analysis indicated that the inhibitory activity of Pelgipeptins in the cell-free supernatant was unaffected during exposure to 60 degrees C for 2 h or a pH ranging from 1.0 to 8.0. Based on the strong antifungal activity and attractive biochemical properties, Pelgipeptins might provide an alternative resource of chemical pesticides for the biocontrol of plant diseases.

SummaryPaenibacillus sp. F6‐B70 was selected from several dozens of isolates with activity against methicillin‐resistant Staphylococcus aureus using a 16S rDNA‐based screening method. F6‐B70 contained polyketide synthase (PKS) and non‐ribosomal peptide synthetase (NRPS) clusters in its genome revealed by PCR amplification of conserved adenylation and ketosynthase (KS) domains. Phylogenetic data suggested that the strain hosts trans‐AT PKSs and their product may be a branched molecule. An antibiotic was subsequently isolated from the methanol extract of F6‐B70 cells. The molecular formula of the antibiotic was deduced to be C33H50NaO6 ([M + Na]+, m/z 565.3505) by analysis of electrospray ionization mass spectral data. Elucidation of the structure by nuclear magnetic resonance and infrared spectroscopy revealed that the active compound, paenimacrolidin (PAM), was a novel 22‐membered macrolide with side‐chains. The new antibiotic, mainly as a bacteriostatic agent, inhibits a couple of multidrug‐resistant Staphylococcus sp. strains. The antibiotic capacity of PAM was compromised by its instability, which can be overcome significantly with addition of an anti‐oxidant. To our knowledge, this is the first report of the isolation of an active macrolide from paenibacilli, which may be a promising source of novel antibiotics.

Two closely related, Gram-stain-negative, rod-shaped, spore-forming strains, B27T and F6-B70,

In a project aiming to isolate strains with the ability to produce nonribosomal peptides, a gram-negative, endospore-forming, rod-shaped strain, designated B5(T), was isolated from a soil sample collected from Tianmu Mountain national natural reserve in Hangzhou, China. Strain B5(T) contained meso-diaminopimelic acid in the cell wall peptidoglycan. The major cellular fatty acids were anteiso-C(15:0) and iso-C(15:0). The DNA G+C content was 42.5 mol%. The phylogenetic analysis based on 16S rRNA gene sequence indicated that strain B5(T) fell within the genus Bacillus, with highest sequence similarity values to Bacillus barbaricus DSM 14730(T) (96.4%) and Bacillus macauensis JCM 13285(T) (95.5%). The isolate, however, could be distinguished from Bacillus strains with validly published names by low 16S rRNA gene sequence similarity values, distinct phenotypic and chemotaxonomic characteristics. On the basis of these polyphasic evidences, it is demonstrated that the isolate B5(T) represents a novel species of the genus Bacillus, for which the name Bacillus tianmuensis sp. nov. is proposed. The type strain is B5(T) (=DSM 22111(T)=CGMCC 1.8879(T)).