Microketides A and B, Polyketides from a Gorgonian-Derived Microsphaeropsis sp. Fungus

Microketides A and B (1 and 2), a pair of new C-11 epimeric polyketides, were obtained from the gorgonian-derived fungus Microsphaeropsis sp. RA10-14 collected from the South China Sea. The absolute configurations of 1 and 2 were assigned by the modified Mosher's method, TDDFT-ECD, and NMR calculations. Compounds 1 and 2 were evaluated for antibacterial, antifungal, and growth inhibition of marine phytoplankton activities. Microketide A (1) exhibited promising inhibitory activity against Pseudomonas aeruginosa, Nocardia brasiliensis, Kocuria rhizophila, and Bacillus anthraci with the same MIC value as ciprofloxacin (0.19 μg/mL).

Rapid and Quantitative Detection of Leifsonia xyli subsp. xyli in Sugarcane Stalk Juice Using a Real-Time Fluorescent (TaqMan) PCR Assay

Ratoon stunting disease (RSD) of sugarcane, one of the most important diseases seriously affecting the productivity of sugarcane crops, was caused by the bacterial agent Leifsonia xyli subsp. xyli (Lxx). A TaqMan probe-based real-time quantitative polymerase chain reaction (qPCR) assay was established in this study for the quantification of Lxx detection in sugarcane stalk juice. A pair of PCR primers (Pat1-QF/Pat1-QR) and a fluorogenic probe (Pat1-QP) targeting the Part1 gene of Lxx were used for the qPCR assay. The assay had a detection limit of 100 copies of plasmid DNA and 100 fg of Lxx genomic DNA, which was 100-fold more sensitive than the conventional PCR. Fifty (28.7%) of 174 stalk juice samples from two field trials were tested to be positive by qPCR assay, whereas, by conventional PCR, only 12.1% (21/174) were tested to be positive with a published primer pair CxxITSf#5/CxxITSr#5 and 15.5% (27/174) were tested to be positive with a newly designed primer pair Pat1-F2/Pat1-R2. The new qPCR assay can be used as an alternative to current diagnostic methods for Lxx, especially when dealing with certificating a large number of healthy cane seedlings and determining disease incidence accurately in commercial fields.

Zhihengliuella halotolerans gen. nov., sp. nov., a novel member of the family Micrococcaceae

The actinobacterial strain YIM 70185T was isolated from a saline soil sample collected from Qinghai province, north-west China, and subjected to a taxonomic investigation. Phylogenetic analysis based on 16S rRNA gene sequences revealed 93.5–96.4 % similarity to members of related genera in the family Micrococcaceae. In the phylogenetic dendrogram based on 16S rRNA gene sequence analysis, strain YIM 70185T formed a separate clade next to the genera Micrococcus and Citricoccus within the family Micrococcaceae. The peptidoglycan type was A4α, l-lys–l-ala–l-Glu. Cell-wall sugars contained glucose and tyvelose. The polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, an unknown phospholipid and an unknown glycolipid. The menaquinones were MK-9, MK-10 and MK-8 (molar ratio 5 : 2 : 1). The major fatty acids were ai-C15 : 0 and i-C15 : 0 and the DNA G+C content was 66.5 mol%. These chemotaxonomic profiles supported the assignment of strain YIM 70185T to a novel genus within the family Micrococcaceae. The name Zhihengliuella halotolerans gen. nov., sp. nov. is proposed. The type strain of Zhihengliuella halotolerans is YIM 70185T (=DSM 17364T=KCTC 19085T).

The hydantoin transport protein from Microbacterium liquefaciens

The gene hyuP from Microbacterium liquefaciens AJ 3912 with an added His6 tag was cloned into the expression plasmid pTTQ18 in an Escherichia coli host strain. The transformed E. coli showed transport of radioisotope-labeled 5-substituted hydantoins with apparent K(m) values in the micromolar range. This activity exhibited a pH optimum of 6.6 and was inhibited by dinitrophenol, indicating the requirement of energy for the transport system. 5-Indolyl methyl hydantoin and 5-benzyl hydantoin were the preferred substrates, with selectivity for a hydrophobic substituent in position 5 of hydantoin and for the l isomer over the d isomer. Hydantoins with less hydrophobic substituents, cytosine, thiamine, uracil, allantoin, adenine, and guanine, were not effective ligands. The His-tagged hydantoin transport protein was located in the inner membrane fraction, from which it was solubilized and purified and its identity was authenticated.

Citricoccus alkalitolerans sp. nov., a novel actinobacterium isolated from a desert soil in Egypt

An actinobacterium, strain YIM 70010T, which was isolated from a desert soil sample collected in Egypt, was subjected to a polyphasic taxonomy study. The organism was alkalitolerant and its optimum growth occurred at pH 8·0–9·0. The isolate contained chemotaxonomic markers that were characteristic of the genus Citricoccus, i.e. the peptidoglycan type Lys–Gly–Glu (variation A4α), the predominant menaquinone MK-9(H2) and a polar lipid profile consisting of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two unknown glycolipids. The major fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The G+C content of the genomic DNA was 63·8 mol%. Strain YIM 70010T exhibited a 16S rRNA gene sequence similarity of 99·6 % and DNA–DNA relatedness value of 56 % with Citricoccus muralis DSM 14442T. The phenotypic characteristics and DNA–DNA relatedness data indicate that strain YIM 70010T can be distinguished from C. muralis (DSM 14442T). Therefore, on the basis of the polyphasic taxonomic data presented, a novel species of the genus Citricoccus, Citricoccus alkalitolerans sp. nov. (type strain, YIM 70010T=CCTCC AA 203008T=DSM 15665T=KCTC 19012T) is proposed.

Reclassification of strain CCM 132, previously classified as Kocuria varians, as Kocuria carniphila sp. nov

A Gram-positive actinobacterium, previously classified as Kocuria varians, was subjected to a polyphasic taxonomic study. The bacterium showed the peptidoglycan type Lys–Ala3 (variation A3α), MK-7(H2) was the major menaquinone and anteiso-C15 : 0 and anteiso-C17 : 0 were the major fatty acids. On the basis of the phylogenetic and phenotypic characteristics of the actinobacterium, a novel species, Kocuria carniphila sp. nov. (type strain, CCM 132T=DSM 16004T), is proposed.

Nesterenkonia sandarakina sp. nov. and Nesterenkonia lutea sp. nov., novel actinobacteria, and emended description of the genus Nesterenkonia

Two novel actinobacteria isolates, designated YIM 70009T and YIM 70081T, were characterized in order to determine their taxonomic position. Cells of strains YIM 70009T and YIM 70081T were cocci, although only the latter were motile. The G+C contents of their DNAs were 64·0 and 64·5 mol%, respectively. On the basis of chemotaxonomic characteristics and 16S rRNA gene sequence analysis, the two isolates were classified in the genus Nesterenkonia. DNA–DNA hybridization and comparison of phenotypic characteristics revealed that strains YIM 70009T and YIM 70081T differed from each other and from known species. Therefore, it is proposed that they represent two separate novel species of the genus Nesterenkonia: Nesterenkonia sandarakina sp. nov. (type strain, YIM 70009T=CCTCC AA 203007T=DSM 15664T=KCTC 19011T) and Nesterenkonia lutea sp. nov. (type strain, YIM 70081T=CCTCC AA 203010T=DSM 15666T=KCTC 19013T).

Structural and serological characterization of the major glycolipid from Rothia mucilaginosa

Structural studies on the major glycolipid isolated from Rothia mucilaginosa were carried out utilising specific chemical degradation, NMR spectroscopy and matrix-assisted laser-desorption/ionization time of flight mass spectrometry (MALDI TOF-MS). The glycolipid was found to be a dimannosylacylmonoglyceride in which the carbohydrate part was the glycerol-linked dimannoside alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->3)-sn-Gro (Man A-Man B-Gro), of which Man B was esterified at O-6 by a fatty acid residue. A second fatty acid substituted the secondary methylene position of the glycerol residue, in contrast to the glycolipid previously found in R. dentocariosa and Saccharopolyspora strains, in which the second fatty acid esterified the primary methylene position of glycerol. Results of the ELISA experiment with rabbit specific antibacterial sera indicate that these two major glycolipids are antigenic, and the patterns of serological reactivity are similar but not identical.

Rhamnolipid biosurfactants produced by Renibacterium salmoninarum 27BN during growth on n-hexadecane

A new strain Renibacterium salmoninarum 27BN was isolated for its capacity to utilize n-hexadecane as sole substrate. Growth on n-hexadecane was accompanied with the production of glycolipid surface active substances detected by surface pressure lowering and emulsifying activity. Glycolipid detection by thin layer chromatography and infrared spectra analyses showed for the first time that Renibacterium salmoninarum 27BN secretes the two rhamnolipids RLL and RRLL typical for Pseudomonas aeruginosa. Growth of Renibacterium salmoninarum 27BN on n-hexadecane depended on the bioavailability of the substrate and the secreted rhamnolipids appeared to be efficient in increasing hexadecane availability for the cells.

Rothia dentocariosa: taxonomy and differential diagnosis

As recent external quality control results have shown, the diagnosis of Rothia dentocariosa infection still presents problems for clinical laboratories. This review describes the taxonomy, as well as the chemotaxonomic, morphological and biochemical characteristics, of this organism, and surveys bacteria that may be confused with Rothia dentocariosa.

Improved production of bioactive glucosylmannosyl-glycerolipid by sponge-associated Microbacterium species

The marine Microbacterium species HP2 (DSM 12583), isolated from the sponge Halichondria panicea, is able to produce a glucosylmannosyl-glycerolipid when grown on a complex medium with glucose. Optimizing the carbon sources in shake flask experiments has shown that glycerol affords the highest specific glycoglycerolipid production. The product yield approached 300 mg/L or 25 mg/g biomass upon scaling up in a 40-L bioreactor volume. The native diglycosyl-glycerolipid GGL.2 strongly inhibited growth of the tumor cell lines HM02 and Hep G2 (50% inhibition at 0.4 to 3 microg/mL), while the related deacylated compound (GG.2) showed a potent anti-tumor-promoting activity.

Nesterenkonia lacusekhoensis sp. nov., isolated from hypersaline Ekho Lake, East Antarctica, and emended description of the genus Nesterenkonia

An aerobic and heterotrophic isolate, designated IFAM EL-30T, was obtained from hypersaline Ekho Lake (Vestfold Hills, East Antarctica). The isolate consisted of Gram-positive cocci or short rods which occasionally exhibited branching. The organism was moderately halotolerant, required thiamin.HCI and was stimulated by biotin and nicotinic acid. It grew well with glucose, acetate, pyruvate, succinate, malate or glutamate, and hydrolysed DNA but not gelatin, starch or Tween 80. Nitrate was aerobically reduced to nitrite. Chemical analysis revealed diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine and an unidentified glycolipid as the major polar lipids. The cellular fatty acids were predominantly of the anteiso and iso methyl-branched types, and the major menaquinone6 were MK-7 and MK-8. The peptidoglycan type was A4alpha, L-Lys-L-Glu. The DNA base ratio was 66.1 mol% G+C. Comparisons of 16S rRNA gene sequences showed that the unidentified organism was phylogenetically closely related to Nesterenkonia halobia, although a sequence divergence value of > 3% demonstrated that the organism represents a different species. On the basis of phenotypic and genotypic evidence, it is proposed that the unknown bacterium be designated as a new species of the genus Nesterenkonia, namely Nesterenkonia lacusekhoensis sp. nov., the type strain being IFAM EL-30T (= DSM 12544T = CIP 107030T). An emended description of the genus Nesterenkonia is given.

Effect of nitrate and nitrite curing salts on microbial changes and sensory quality of non-fermented sausages

The effects of nitrate and nitrite curing salts on microbial changes and sensory quality of non-fermented sausages of small diameter were investigated. During pre-ripening (day 5), levels of lactic acid bacteria and yeasts were slightly higher in nitrite-made sausages than in those made with nitrate. In contrast, nitrite discouraged the growth of psychrotrophs as occurs in fermented sausages. By the end of ripening (day 26), levels of microorganisms were similar in both batches of sausages except for psychrotrophs being higher in those made with nitrite. Nitrate-made sausages showed higher aroma and taste intensity.

Polyphasic taxonomy of Nesterenkonia halobia

A phenotypic study has been carried out on six moderately halophilic gram-positive nonmotile cocci isolated from ponds of a saltern located in Huelva, Spain. These strains were examined for 150 morphological, physiological, biochemical, and nutritional traits and showed phenotypic characteristics similar to those of Nesterenkonia halobia (formerly Micrococcus halobius). The guanine-plus-cytosine (G + C) content of their DNA ranged between 70 and 72 mol%, values quite similar to those described for N. halobia (71.5 mol%). The 16S rDNA sequence analysis of one representative isolate showed that it is phylogenetically quite close to N. halobia, within the high-G + C-content gram-positive branch. DNA-DNA hybridization experiments showed a high degree of homology (72 to 100%) among the six isolates and the type strain N. halobia ATCC 21727. All data demonstrate quite clearly that the six isolates are members of the species N. halobia. Since this species was described on the basis of a single strain isolated from unrefined solar salt, and its description is not complete (especially in the utilization of different compounds), our study contributes to a better description of the moderate halophile N. halobia.

Stomatococcus mucilaginosus produces a mannose-containing lipoglycan rather than lipoteichoic acid

Five strains of Stomatococcus mucilaginosus were investigated to determine whether the organism produces a lipoteichoic acid or a lipoglycan. Crude phenol extracts were purified by hydrophobic interaction chromatography and shown to contain lipoglycan. The major carbohydrate component present was mannose, indicating that the macroamphiphile is a lipomannan. The fatty acid composition of the lipoglycan was similar to that of stomatococcal whole cells. These data provide additional chemotaxonomic evidence supporting the suprageneric classification of the genus Stomatococcus within a group of actinomycete genera that also includes the genus Micrococcus.

Bacteremia caused by Stomatococcus mucilaginosus: report of seven cases and review of the literature

During a three-year period eight patients with blood cultures positive for Stomatococcus mucilaginosus were identified at two university hospitals. One patient without any signs of infection had a central venous catheter that was colonized with this organism, two patients had transient bacteremia without definite relationship to underlying disease, whereas the remaining five patients suffered from clinically significant infections. Of these last five patients, one had undergone prior head and neck surgery and four had hematologic malignancy with mild to severe neutropenia; two of the latter patients developed the infection subsequent to dental surgery. Besides neutropenia and mucosal damage in the oropharynx, quinolone antibacterial prophylaxis may have been an additional risk factor for the development of S. mucilaginosus bacteremia in these patients. A thorough review of the literature revealed that in addition to our findings, endocarditis and foreign body infections are further typical clinical manifestations. Although the overall antibiotic susceptibility pattern of S. mucilaginosus resembles that of streptococci, it is suggested that penicillin G may not be the drug of choice for initial therapy of particularly severe infections. S. mucilaginosus can be easily differentiated from other gram-positive bacteria when certain key criteria (e.g. adherence to agar surfaces, poor growth on Mueller-Hinton agar, presence of a capsule) as well as an array of biochemical tests, including commercially available identification systems, are applied. Our own and published data emphasize that both microbiologists and clinicians should be increasingly aware of this opportunistic pathogen.