Frequency of three mutations in the fumonisin biosynthetic gene cluster of Fusarium fujikuroi that are predicted to block fumonisin production

Fusarium fujikuroi is the most prominent pathogen found in rice. In addition to gibberellin, F. fujikuroi produces various secondary metabolites, including the polyketide mycotoxins, fumonisins. Fumonisin production is conferred by the fumonisin biosynthetic gene (FUM) cluster consisting of 15-17 genes. F. fujikuroi is phylogenetically subclassified into one group with fumonisin production (F-group) and another group in which fumonisin production is undetectable (G-group). In a previous study, a G-to-T substitution (FUM21_G2551T) in the FUM cluster transcription factor gene, FUM21, was identified as a cause of fumonisin-non-production in a G-group strain. In the current study, further analysis of G-group strains identified two additional mutations that involved FUM-cluster genes essential for fumonisin production: (1) a 22.4-kbp deletion in the FUM10-FUM19 region; and (2) a 1.4-kbp insertion in FUM6. PCR analysis of 44 G-group strains, indicated that 84% had the FUM21_G2551T mutation, 50% had the 22.4-kbp FUM10-FUM19 deletion, and 32% had the 1.4-kbp insertion in FUM6, and some strains had two or all the mutations. None of the mutations were detected in the 51 F-group strains examined. Each of the three mutations alone could account for the lack of fumonisin production in G-group strains. However, one G-group strain did not have any of the mutations. Therefore, another mutation(s) is likely responsible for the lack of fumonisin production in some G-group strains of F. fujikuroi.

Closed Genome Sequence of Escherichia coli K-12 Group Strain C600

Escherichia coli strain C600 is a prototypical K-12 derived laboratory strain which has been broadly used for molecular microbiology and bacterial physiology studies since its isolation in 1954. Here, we present the closed genome sequence of E. coli strain C600, retrieved from the American Type Culture Collection (ATCC 23724).

Classification of organisms previously reported as the SP and Stewart–Letscher groups, with descriptions of Necropsobacter gen. nov. and of Necropsobacter rosorum sp. nov. for organisms of the SP group

To allow classification of bacteria previously reported as the SP group and the Stewart–Letscher group, 35 isolates from rodents (21), rabbits (eight), a dog and humans (five) were phenotypically and genotypically characterized. Comparison of partial rpoB sequences showed that 34 of the isolates were closely related, demonstrating at least 97.4 % similarity. 16S rRNA gene sequence comparison of 20 selected isolates confirmed the monophyly of the SP group and revealed 98.5 %–100 % similarity between isolates. A blast search using the 16S rRNA gene sequences showed that the highest similarity outside the SP group was 95.5 % to an unclassified rat isolate. The single strain, P625, representing the Stewart–Letscher group showed the highest 16S rRNA gene similarity (94.9–95.5 %) to members of the SP group. recN gene sequence analysis of 11 representative strains resulted in similarities of 97–100 % among the SP group strains, which showed 80 % sequence similarity to the Stewart–Letscher group strain. Sequence similarity values based on the recN gene, indicative for whole genome similarity, showed the SP group being clearly separated from established genera, whereas the Stewart–Letscher group strain was associated with the SP group. A new genus, Necropsobacter gen. nov., with only one species, Necropsobacter rosorum sp. nov., is proposed to include all members of the SP group. The new genus can be separated from existing genera of the family Pasteurellaceae by at least three phenotypic characters. The most characteristic properties of the new genus are that haemolysis is not observed on bovine blood agar, positive reactions are observed in the porphyrin test, acid is produced from (+)-l-arabinose, (+)-d-xylose, dulcitol, (+)-d-galactose, (+)-d-mannose, maltose and melibiose, and negative reactions are observed for symbiotic growth, urease, ornithine decarboxylase and indole. Previous publications have documented that both ubiquinones and demethylmenaquinone were produced by the proposed type strain of the new genus, Michel A/76T, and that the major polyamine of representative strains (type strain not included) of the genus is 1,3-diaminopropane, spermidine is present in moderate amounts and putrescine and spermine are detectable only in minor amounts. The major fatty acids of strain Michel A/76T are C14 : 0, C16 : 0, C16:1ω7c and summed feature C14 : 0 3-OH/iso-C16 : 1 I. This fatty acid profile is typical for members of the family Pasteurellaceae. The G+C content of DNA of strain Michel A/76T was estimated to be 52.5 mol% in a previous investigation. The type strain is P709T ( = Michel A/76T = CCUG 28028T = CIP 110147T = CCM 7802T).

Marinicola seohaensis gen. nov., sp. nov., isolated from sea water of the Yellow Sea, Korea

A Gram-negative, non-flagellated, non-spore-forming and rod-shaped bacterial strain, SW-152T, was isolated from sea water of the Yellow Sea in Korea, and subjected to a polyphasic taxonomic study. Strain SW-152T grew optimally at 30 °C and in the presence of 2–3 % (w/v) NaCl. It contained MK-7 as the predominant menaquinone and iso-C15 : 0 and iso-C15 : 1 as the major fatty acids. Polar lipids detected in strain SW-152T were phosphatidylethanolamine, diphosphatidylglycerol and unidentified lipids. The DNA G+C content was 40·3 mol%. Phylogenetic trees based on 16S rRNA gene sequences exhibited that strain SW-152T forms a distinct evolutionary lineage within the Cytophaga–Flavobacterium–Bacteroides (CFB) group. Strain SW-152T exhibited low 16S rRNA similarity levels of less than 89·4 % to members belonging to the CFB group. Phenotypic properties of strain SW-152T differentiate it from phylogenetically related taxa. On the basis of phenotypic and phylogenetic data, strain SW-152T (=KCTC 12312T=JCM 12600T) was classified in a novel genus and species, Marinicola seohaensis gen. nov., sp. nov.