A bacterial cytokine

Viable cells of Micrococcus luteus secrete a factor, which promotes the resuscitation and growth of dormant, nongrowing cells of the same organism. The resuscitation-promoting factor (Rpf) is a protein, which has been purified to homogeneity. In picomolar concentrations, it increases the viable cell count of dormant M. luteus cultures at least 100-fold and can also stimulate the growth of viable cells. Rpf also stimulates the growth of several other high G+C Gram-positive organisms, including Mycobacterium avium, Mycobacterium bovis (BCG), Mycobacterium kansasii, Mycobacterium smegmatis, and Mycobacterium tuberculosis. Similar genes are widely distributed among high G+C Gram-positive bacteria; genome sequencing has uncovered examples in Mycobacterium leprae and Mb. tuberculosis and others have been detected by hybridization in Mb. smegmatis, Corynebacterium glutamicum, and Streptomyces spp. The mycobacterial gene products may provide different targets for the detection and control of these important pathogens. This report is thus a description of a proteinaceous autocrine or paracrine bacterial growth factor or cytokine.

A family of autocrine growth factors in Mycobacterium tuberculosis

Mycobacterium tuberculosis and its close relative, Mycobacterium bovis (BCG) contain five genes whose predicted products resemble Rpf from Micrococcus luteus. Rpf is a secreted growth factor, active at picomolar concentrations, which is required for the growth of vegetative cells in minimal media at very low inoculum densities, as well as the resuscitation of dormant cells. We show here that the five cognate proteins from M. tuberculosis have very similar characteristics and properties to those of Rpf. They too stimulate bacterial growth at picomolar (and in some cases, subpicomolar) concentrations. Several lines of evidence indicate that they exert their activity from an extra-cytoplasmic location, suggesting that they are also involved in intercellular signalling. The five M. tuberculosis proteins show cross-species activity against M. luteus, Mycobacterium smegmatis and M. bovis (BCG). Actively growing cells of M. bovis (BCG) do not respond to these proteins, whereas bacteria exposed to a prolonged stationary phase do. Affinity-purified antibodies inhibit bacterial growth in vitro, suggesting that sequestration of these proteins at the cell surface might provide a means to limit or even prevent bacterial multiplication in vivo. The Rpf family of bacterial growth factors may therefore provide novel opportunities for preventing and controlling mycobacterial infections.

Multiparameter flow cytometric analysis of antibiotic effects on membrane potential, membrane permeability, and bacterial counts of Staphylococcus aureus and Micrococcus luteus

Although flow cytometry has been used to study antibiotic effects on bacterial membrane potential (MP) and membrane permeability, flow cytometric results are not always well correlated to changes in bacterial counts. Using new, precise techniques, we simultaneously measured MP, membrane permeability, and particle counts of antibiotic-treated and untreated Staphylococcus aureus and Micrococcus luteus cells. MP was calculated from the ratio of red and green fluorescence of diethyloxacarbocyanine [DiOC(2)(3)]. A normalized permeability parameter was calculated from the ratio of far red fluorescence of the nucleic acid dye TO-PRO-3 and green DiOC(2)(3) fluorescence. Bacterial counts were calculated by the addition of polystyrene beads to the sample at a known concentration. Amoxicillin increased permeability within 45 min. At concentrations of <1 microg/ml, some organisms showed increased permeability but normal MP; this population disappeared after 4 h, while bacterial counts increased. At amoxicillin concentrations above 1 microg/ml, MP decreased irreversibly and the particle counts did not increase. Tetracycline and erythromycin caused smaller, dose- and time-dependent decreases in MP. Tetracycline concentrations of <1 microg/ml did not change permeability, while a tetracycline concentration of 4 microg/ml permeabilized 50% of the bacteria; 4 microg of erythromycin per ml permeabilized 20% of the bacteria. Streptomycin decreased MP substantially, with no effect on permeability; chloramphenicol did not change either permeability or MP. Erythromycin pretreatment of bacteria prevented streptomycin and amoxicillin effects. Flow cytometry provides a sensitive means of monitoring the dynamic cellular events that occur in bacteria exposed to antibacterial agents; however, it is probably simplistic to expect that changes in a single cellular parameter will suffice to determine the sensitivities of all species to all drugs.

The rpf gene of Micrococcus luteus encodes an essential secreted growth factor

Micrococcus luteus secretes a small protein called Rpf, which has autocrine and paracrine signalling functions and is required for the resuscitation of dormant cells. Originally isolated from the supernatant of actively growing cultures, Rpf was also detected on the surface of actively growing bacteria. Most molecules may be sequestered non-productively at the cell surface, as a truncated form of the protein, encompassing only the 'Rpf domain' is fully active. The C-terminal LysM module, which probably mediates binding to the cell envelope, is not required for biological activity. Rpf was essential for growth of M. luteus. Washed cells, inoculated at low density into a minimal medium, could not grow in its absence. Moreover, the incorporation of anti-Rpf antibodies into the culture medium at the time of inoculation also prevented bacterial growth. We were unable to inactivate rpf using a disrupted form of the gene, in which most of the coding sequence was replaced with a selectable thiostrepton resistance marker. Gene disruption was possible in the presence of a second, functional, plasmid-located copy of rpf, but not in the presence of a rpf derivative whose protein product lacked the secretory signal sequence. As far as we are aware, Rpf is the first example of a truly secreted protein that is essential for bacterial growth. If the Rpf-like proteins elaborated by Mycobacterium tuberculosis and other mycobacteria prove similarly essential, interference with their proper functioning may offer novel opportunities for protecting against, and treating, tuberculosis and other mycobacterial disease.

Optimization of annealing temperature to reduce bias caused by a primer mismatch in multitemplate PCR

To reduce PCR bias derived from a primer mismatch, the effect of the annealing temperature on the product ratio was investigated by denaturing gradient gel electrophoresis analysis of PCR products from a mixture of perfect-match and one-mismatch templates. These templates were generated by PCR from Pediococcus acidilactici for one mismatch and Micrococcus luteus for the perfect match. PCRs showed that the bias was reduced at lower temperatures. An environmental sample was also examined.

Dependence of the Raman signature of genomic B-DNA on nucleotide base sequence

The vibrational spectra of four genomic and two synthetic DNAs, encompassing a wide range in base composition [poly(dA-dT). poly(dA-dT), 0% G + C; Clostridium perfringens DNA, 27% G + C; calf thymus DNA, 42% G + C; Escherichia coli DNA, 50% G + C; Micrococcus luteus DNA, 72% G + C; poly(dG-dC).poly(dG-dC), 100% G + C] (dA: deoxyadenosine; dG: deoxyguanosine; dC: deoxycytidine; dT: thymidine), have been analyzed using Raman difference methods of high sensitivity. The results show that the Raman signature of B DNA depends in detail upon both genomic base composition and sequence. Raman bands assigned to vibrational modes of the deoxyribose-phosphate backbone are among the most sensitive to base sequence, indicating that within the B family of conformations major differences occur in the backbone geometry of AT- and GC-rich domains. Raman bands assigned to in-plane vibrations of the purine and pyrimidine bases-particularly of A and T-exhibit large deviations from the patterns expected for random base distributions, establishing that Raman hypochromic effects in genomic DNA are also highly sequence dependent. The present study provides a basis for future use of Raman spectroscopy to analyze sequence-specific DNA-ligand interactions. The demonstration of sequence dependency in the Raman spectrum of genomic B DNA also implies the capability to distinguish genomic DNAs by means of their characteristic Raman signatures.

Isolation and structure of an intrastrand cross-link adduct of mitomycin C and DNA

A new covalent mitomycin C-DNA adduct (4) was isolated from DNA exposed to reductively activated mitomycin C (MC) in vitro. The MC-treated DNA was hydrolyzed enzymatically under certain conditions, and the new adduct was isolated from the hydrolysate by HPLC. Its structure was determined by ultraviolet and circular dichroism spectroscopy and chemical and enzymatic transformations conducted on microscale. In the structure, a single 2" beta, 7"-diaminomitosene residue is linked bifunctionally to two guanines in the dinucleoside phosphate d(GpG). The guanines are linked at their N2 atoms to the C1" and C10" positions of the mitosene, respectively. A key to the structure was a finding that removal of the mitosene from the adduct by hot piperidine yielded d(GpG); another was that the adduct was slowly converted to the known interstrand cross-link adduct 3 by snake venom diesterase and alkaline phosphatase. Adduct 4 represents an intrastrand cross-link in DNA formed by MC. Of the two possible strand-polarity isomers of 4, 4a in which the mitosene 1"-position is linked to the 3'-guanine of d(GpG) is designated as the proper structure, on the basis of the mechanism of the cross-linking reaction. The same adduct 4 was isolated from poly(dG).poly(dC), synthetic oligonucleotides containing the GpG sequence, and Micrococcus luteus and calf thymus DNAs. The relative yields of interstrand and intrastrand cross-links (3 and 4) were determined under first-order kinetic conditions; an average 3.6-fold preference for the formation of 3 over that of 4 was observed. An explanation for this preference is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Micrococcus luteus -- survival in amber

A growing body of evidence now supports the isolation of microorganisms from ancient materials. However, questions about the stringency of extraction methods and the genetic relatedness of isolated organisms to their closest living relatives continue to challenge the authenticity of these ancient life forms. Previous studies have successfully isolated a number of spore-forming bacteria from organic and inorganic deposits of considerable age whose survival is explained by their ability to enter suspended animation for extended periods of time. However, despite a number of putative reports, the isolation of non-spore-forming bacteria and an explanation for their survival have remained enigmatic. Here we describe the isolation of non-spore-forming cocci from a 120-million-year-old block of amber, which by genetic, morphological, and biochemical analyses are identified as belonging to the bacterial species Micrococcus luteus. Although comparison of 16S rRNA sequences from the ancient isolates with their modern counterparts is unable to confirm the precise age of these bacteria, we demonstrate, using complementary molecular and cell biological techniques, evidence supporting the view that these (and related modern members of the genus) have numerous adaptations for survival in extreme, nutrient-poor environments, traits that will assist in this bacteria's persistence and dispersal in the environment. The bacteria's ability to utilize succinic acid and process terpine-related compounds, both major components of natural amber, support its survival in this oligotrophic environment.

Isolation and molecular detection of methylotrophic bacteria occurring in the human mouth

Diverse methylotrophic bacteria were isolated from the tongue, and supra- and subgingival plaque in the mouths of volunteers and patients with periodontitis. One-carbon compounds such as dimethylsulfide in the mouth are likely to be used as growth substrates for these organisms. Methylotrophic strains of Bacillus, Brevibacterium casei, Hyphomicrobium sulfonivorans, Methylobacterium, Micrococcus luteus and Variovorax paradoxus were characterized physiologically and by their 16S rRNA gene sequences. The type strain of B. casei was shown to be methylotrophic. Enzymes of methylotrophic metabolism were characterized in some strains, and activities consistent with growth using known pathways of C1-compound metabolism demonstrated. Genomic DNA from 18 tongue and dental plaque samples from nine volunteers was amplified by the polymerase chain reaction using primers for the 16S rRNA gene of Methylobacterium and the mxaF gene of methanol dehydrogenase. MxaF was detected in all nine volunteers, and Methylobacterium was detected in seven. Methylotrophic activity is thus a feature of the oral bacterial community.

A promoter associated with the neisserial repeat can be used to transcribe the uvrB gene from Neisseria gonorrhoeae

A recombinant plasmid capable of restoring UV resistance to an Escherichia coli uvrB mutant was isolated from a genomic library of Neisseria gonorrhoeae. Sequence analysis revealed an open reading frame whose deduced amino acid sequence displayed significant similarity to those of the UvrB proteins of E. coli, Micrococcus luteus, and Streptococcus pneumoniae. A gonococcal uvrB mutant was constructed and found to be extremely sensitive to UV radiation. Transcriptional fusions between portions of the gonococcal uvrB upstream region and a reporter gene were used to localize promoter activity, and the transcriptional start point of the gonococcal uvrB gene was mapped in E. coli by primer extension. A corresponding sigma 70 promoter was identified within a copy of the 26-bp neisserial repeat, and this identification provided the first evidence of a promoter associated with this repetitive element in N. gonorrhoeae.

Purification and cloning of Micrococcus luteus ultraviolet endonuclease, an N-glycosylase/abasic lyase that proceeds via an imino enzyme-DNA intermediate

Although Micrococcus luteus UV endonuclease has been reported to be an 18-kDa enzyme with possible homology to the 16-kDa endonuclease V from bacteriophage T4 (Gordon, L. K., and Haseltine, W. A. (1980) J. Biol. Chem. 255, 12047-12050; Grafstrom, R. H., Park, L., and Grossman, L. (1982) J. Biol. Chem. 257, 13465-13474), this study describes three independent purification schemes in which M. luteus UV damage-specific or pyrimidine dimer-specific nicking activity was associated with two proteins of apparent molecular masses of 31 and 32 kDa. An 18-kDa contaminant copurified with the doublet through many of the chromatographic steps, but it was determined to be a homolog of Escherichia coli ribosomal protein L6. Edman degradation analyses of the active proteins yielded identical NH2-terminal amino acid sequences. The corresponding gene (pdg, pyrimidine dimer glycosylase) was cloned. The protein bears strong sequence similarities to the E. coli repair proteins endonuclease III and MutY. Nonetheless, traditionally purified M. luteus protein acted exclusively on cis-syn thymine dimers; it was unable to cleave site-specific oligonucleotide substrates containing a trans-syn -I, (6-4), or Dewar thymine dimer, a 5,6-dihydrouracil lesion, or an A:G or A:C mismatch. The UV endonuclease incised cis-syn dimer-containing DNA in a dose-dependent manner and exhibited linear kinetics within that dose range. Enzyme activity was inhibited by the presence of NaCN or NaBH4 with NaBH4 additionally being able to trap a covalent enzyme-substrate product. These last findings confirm that the catalytic mechanism of M. luteus UV endonuclease, like those of other glycosylase/AP lyases, involves an imino intermediate.

Reclassification of ATCC 9341 from Micrococcus luteus to Kocuria rhizophila

Strain ATCC 9341, currently known as Micrococcus luteus, has been designated as a quality-control strain in a number of applications. It is also cited as the standard culture in several official methods and manuals, as well as the Code of Federal Regulations. Over the years, it has become apparent that ATCC 9341 does not resemble other M. luteus strains; however, its phenotypic characteristics alone were ambiguous. Recently, a polyphasic study was performed in which molecular data were combined with cytochemical properties and physiological characteristics. The results clearly indicate that ATCC 9341 is a member of the genus Kocuria. Thus, it is proposed to reclassify ATCC 9341 as Kocuria rhizophila and to alert users worldwide of this name change.

The effect of ribosomal protein S1 from Escherichia coli and Micrococcus luteus on protein synthesis in vitro by E. coli and Bacillus subtilis

We have designed a set of nine plasmids containing the Bacillus pumilis cat gene with one of three Shine-Dalgarno (SD) sequences (weak, strong or stronger) and one of three initiation codons (AUG, GUG or UUG). These constructions have been used to determine the effect of ribosomal protein S1, SD and initiation codon sequences and Escherichia coli ribosomal protein S1 on translation in vitro by E. coli and B. subtilis ribosomes. Translation of these nine constructions was determined with three types of ribosomes: E. coli containing ribosomal protein S1, E. coli depleted of S1, and B. subtilis which is naturally free of S1. E. coli ribosomes were able to translate all nine transcripts with variable efficiencies. B. subtilis and S1-depleted E. coli ribosomes were similar to each other and differed from non-depleted E. coli ribosomes in that they required strong or stronger SD sequences and were unable to translate any of the weak transcripts. Addition of S1 from either E. coli or Micrococcus luteus, a Gram-positive bacterium, enabled S1-depleted E. coli ribosomes to translate mRNAs with weak SD sequences but had no effect on B. subtilis ribosomes. AUG was the preferred initiation codon for all ribosome types; however, B. subtilis ribosomes showed greater tolerance for the non-AUG codons than either type of E. coli ribosome. The presence of a strong or stronger SD sequence increased the efficiency by which E. coli ribosomes could utilize non-AUG codons.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential of Mycobacterium tuberculosis resuscitation-promoting factors as antigens in novel tuberculosis sub-unit vaccines

Novel vaccines are needed to control tuberculosis (TB), the bacterial infectious disease that together with malaria and HIV is worldwide responsible for high levels of morbidity and mortality. TB can result from the reactivation of an initially controlled latent infection by Mycobacterium tuberculosis (Mtb). Mtb proteins for which a possible role in this reactivation process has been hypothesized are the five homologs of the resuscitation-promoting factor of Micrococcus luteus, namely Mtb Rv0867c (rpfA), Rv1009 (rpfB), Rv1884c (rpfC), Rv2389c (rpfD) and Rv2450c (rpfE). Analysis of the immune recognition of these 5 proteins following Mtb infection or Mycobacterium bovis BCG vaccination of mice showed that Rv1009 (rpfB) and Rv2389c (rpfD) are the most antigenic in the tested models. We therefore selected rpfB and rpfD for testing their vaccine potential as plasmid DNA vaccines. Elevated cellular immune responses and modest but significant protection against intra-tracheal Mtb challenge were induced by immunization with the rpfB encoding DNA vaccine. The results indicate that rpfB is the most promising candidate of the five rpf-like proteins of Mtb in terms of its immunogenicity and protective efficacy and warrants further analysis for inclusion as an antigen in novel TB vaccines.

Structure of the dnaA and DnaA-box region in the Mycoplasma capricolum chromosome: conservation and variations in the course of evolution

We have previously shown that the dnaA gene and the DnaA-box region were conserved in bacteria representative of all three major branches of the eubacterial phylogenic tree: high G + C Gram+, low-G + C Gram+ and Gram-. In the present work, we determined the structure of the dnaA region of Mycoplasma capricolum and found that the dnaA gene and at least two other genes, rpmH and dnaN, were conserved in this bacterium. An unusually high level of amino acid (aa) substitutions was observed in M. capricolum DnaA. It was the case even in those aa which were well conserved in other bacterial species. The nontranslatable region upstream from the dnaA gene was also conserved in this bacterium, as it was universally found in both Gram+ and Gram- bacteria. An additional nontranslatable region downstream from the dnaA gene, which is common to Gram+ bacteria, was also found in M. capricolum, consistent with the proposal that M. capricolum is Gram+ in origin. These regions were rich in A + T and contained ten DnaA-box-like sequences (9-mers that differ from TTATCCACA by one or two bases).

β-Lactone Synthetase Found in the Olefin Biosynthesis Pathway

The first β-lactone synthetase enzyme is reported, creating an unexpected link between the biosynthesis of olefinic hydrocarbons and highly functionalized natural products. The enzyme OleC, involved in the microbial biosynthesis of long-chain olefinic hydrocarbons, reacts with syn- and anti-β-hydroxy acid substrates to yield cis- and trans-β-lactones, respectively. Protein sequence comparisons reveal that enzymes homologous to OleC are encoded in natural product gene clusters that generate β-lactone rings, suggesting a common mechanism of biosynthesis.

Presence of a gene in the archaebacterium Methanococcus vannielii homologous to secY of eubacteria

The nucleotide sequence of a gene located at the promoter-distal side of the 'spectinomycin-operon' homologue of the archaebacterium Methanococcus vannielii was determined. Its derived amino acid sequence displayed 20% (identical positions) or 52% (including conservative exchanges) similarity, respectively, to SECY from E coli. An alignment of the Methanococcus SECY with eubacterial SECY sequences showed the existence of 10 membrane-associated primary structure domains in equivalent positions. The 5' and 3' ends of the secY transcript were mapped and the gene was expressed in the T7 promoter/polymerase system in E col. The temperature-sensitive growth of the E coli mutant IQ292 which harbours a secYts mutation could be complemented by the secY gene from Methanococcus. This indicates that a protein integral to an archaebacterial ether-lipid membrane can be inserted into a eubacterial phospholipid membrane without apparent loss of function.

Transcription termination factor Rho is essential for Micrococcus luteus

The growth of Micrococcus luteus, a soil microorganism that belongs to the high-G+C gram-positive phylogenetic group, is prevented by bicyclomycin, an antibiotic that inhibits the activity of the M. luteus transcription termination factor Rho. A mutant that can grow in 0.3 mM bicyclomycin has a Rho that is insensitive to bicyclomycin and has the single amino acid residue change of Asp474 to Gly. These results indicate that the function of its Rho factor is essential for M. luteus and that growth of a gram-positive organism can be blocked by bicyclomycin.

Effect of plant age on endophytic bacterial diversity of balloon flower (Platycodon grandiflorum) root and their antimicrobial activities

Balloon flower (Platycodon grandiflorum) is widely cultivated vegetable and used as a remedy for asthma in East Asia. Experiments were conducted to isolate endophytic bacteria from 1-, 3-, and 6-year-old balloon flower roots and to analyze the enzymatic, antifungal, and anti-human pathogenic activities of the potential endophytic biocontrol agents obtained. Total 120 bacterial colonies were isolated from the interior of all balloon flower roots samples. Phylogenetic analysis based on 16S rRNA gene sequences showed that the population of 'low G + C gram-positive bacteria' (LGCGPB) gradually increased 60.0-80.0% from 1 to 6 years balloon flower sample. On the other hand, maximum hydrolytic enzyme activity showing endophytic bacteria was under LGCGPB, among the bacterial strains, Bacillus sp. (BF1-1 and BF3-8), Bacillus sp. (BF1-2 and BF3-5), and Bacillus sp. (BF1-3, BF3-6, and BF6-4) showed maximum enzyme activities. Besides, Bacillus licheniformis (BF3-5 and BF6-6) and Bacillus pumilus (BF6-1) showed maximum antifungal activity against Phytophthora capsici, Fusarium oxysporum, Rhizoctonia solani, and Pythium ultimum. Moreover, Bacillus licheniformis was found in 3 and 6 years balloon flower roots, but Bacillus pumilus was found only in 6 years sample. It is presumed that older balloon flower plants invite more potential antifungal endophytes for there protection from plant diseases. In addition, Bacillus sp. (BF1-2 and BF3-5) showed maximum anti-human pathogenic activity. So, plant age is presumed to influence diversity of balloon flower endophytic bacteria.

Molecular cloning, expression, and characterization of the genes encoding the two essential protein components of Micrococcus luteus B-P 26 hexaprenyl diphosphate synthase

The structural genes encoding the two essential components A and B of hexaprenyl diphosphate synthase, which produce the precursor of the prenyl side chain of menaquinone-6, were cloned from Micrococcus luteus B-P 26.

Novel anticodon composition of transfer RNAs in Micrococcus luteus, a bacterium with a high genomic G + C content. Correlation with codon usage

The number and relative amount of isoacceptor tRNAs for each amino acid in Micrococcus luteus, a Gram-positive bacterium with high genomic G + C content, have been determined by sequencing their anticodon loop and its adjacent regions and by selective labelling of tRNAs. Thirty-one tRNA species with 29 different anticodon sequences have been detected. All the tRNAs have G or C at the anticodon first position except for tRNA(ICGArg) and tRNA(NGASer), in response to the abundant usage of NNC and NNG codons. No tRNA with the anticodon UNN capable of translating codon NNA has been detected, in accordance with a very low or zero usage of NNA codons. The relative amount of isoacceptor tRNAs for an amino acid determined by selective labelling strongly correlates with usage of the corresponding codons. On the basis of these and other observations in this and other eubacterial species, we conclude that the relative amount and anticodon composition of isoacceptor tRNA species are flexible, and their changes are mainly adaptive phenomena that have been primarily affected by codon usage, which in turn is affected by directional mutation pressure.

DNA buoyant density shifts during 15N-DNA stable isotope probing

DNA-based stable isotope probing (SIP) is a novel technique for the identification of organisms actively assimilating isotopically labeled compounds. Herein, we define the limitations to using 15N-labeled substrates for SIP and propose modifications to compensate for these shortcomings. Changes in DNA buoyant density (BD) resulting from 15N incorporation were determined using cultures of disparate GC content (Escherichia coli and Micrococcus luteus). Incorporation of 15N into DNA increased BD by 0.015+/-0.002 g mL(-1) for E. coli and 0.013+/-0.002 g mL(-1) for M. luteus. The DNA BD shift was greatly increased (0.045 g mL(-1)) when dual isotope (13C plus 15N) labeling was employed. Despite the limited DNA BD shift following 15N enrichment, we found the use of gradient fractionation, followed by a comparison of T-RFLP profiles from fractions of labeled and control treatments, facilitated detection of enrichment in DNA samples from either cultures or soil.

Microbial production of aliphatic (S)-epoxyalkanes by using Rhodococcus sp. strain ST-10 styrene monooxygenase expressed in organic-solvent-tolerant Kocuria rhizophila DC2201

We describe the development of biocatalysis for producing optically pure straight-chain (S)-epoxyalkanes using styrene monooxygenase of Rhodococcus sp. strain ST-10 (RhSMO). RhSMO was expressed in the organic solvent-tolerant microorganism Kocuria rhizophila DC2201, and the bioconversion reaction was performed in an organic solvent-water biphasic reaction system. The biocatalytic process enantioselectively converted linear terminal alkenes to their corresponding (S)-epoxyalkanes using glucose and molecular oxygen. When 1-heptene and 6-chloro-1-hexene were used as substrates (400 mM) under optimized conditions, 88.3 mM (S)-1,2-epoxyheptane and 246.5 mM (S)-1,2-epoxy-6-chlorohexane, respectively, accumulated in the organic phase with good enantiomeric excess (ee; 84.2 and 95.5%). The biocatalysis showed broad substrate specificity toward various aliphatic alkenes, including functionalized and unfunctionalized alkenes, with good to excellent ee. Here, we demonstrate that this biocatalytic system is environmentally friendly and useful for producing various enantiopure (S)-epoxyalkanes.

Biofilms on tracheoesophageal voice prostheses: a confocal laser scanning microscopy demonstration of mixed bacterial and yeast biofilms

The aim of this study was to demonstrate the presence of yeast and bacterial biofilms on the surface of tracheoesophageal voice prostheses (TVPs) by a double-staining technique with confocal laser scanning microscopy (CLSM). Biofilms of 12 removed TVPs were visualized by scanning electron microscopy, then stained with ConA-FITC and propidium iodide for CLSM. Microbial identification was by partial 16S rRNA gene analysis and ITS-2 sequence analysis. Microbial biofilms on the TVPs consisted of bacteria and filamentous cells. Bacterial cells were attached to the filamentous and unicellular yeast cells, thus forming a network. Sequence analyses of six voice prostheses identified the presence of a variety of bacterial and yeast species. In vivo studies showed that Klebsiella oxytoca and Micrococcus luteus efficiently attached to Candida albicans. CLSM with double fluorescence staining can be used to demonstrate biofilm formations composed of a mixture of yeast and bacterial cells on the surface of TVPs.