Isolation and study of a strain of Candida tropicalis growing on n-alkanes

Summary A strain of Candida tropicalis has been isolated from soil using a mineral medium that contained n-tetradecane as sole source of carbon. This strain has been studied and variants have been isolated. In contrast to the original strain in which hydrocarbon degradation is linked to enzymatic induction mechanisms, the variant 101 behaves like a constitutive strain for n-tetradecane.     

Genetic stability of the antagonistic character ofEnterococcus faecalis ssp.liquefaciens and the detection of a new inhibitory bacteriocin-like substance

The inhibitory capacity of strain S-48 ofEnterococcus faecalis ssp.liquefaciens was studied. The strain produces a broad-spectrum peptide antibiotic (AS-48) that has been characterized elsewhere. The isolation of mutants from S-48 after mutagenic treatment revealed another inhibitory substance which remained masked in the wild strain. The protein nature and restricted spectrum of this substance points to its being a bacteriocin (Bc-48).     

Efficient transformation and expression of the glucanase gene from Bacillus megaterium in the biocontrol strain Streptomyces lydicus A02

Streptomyces have been used extensively as the biocontrol agents due to their ability to produce various antimicrobial compounds, such as antibiotics and hydrolytic enzymes. Streptomyces lydicus strain A02, which was isolated from the soil of suburban forest field in Beijing (China), is capable of producing natamycin and has proved to be a potential biocontrol agent to several plant fungal diseases, including wilts caused by Fusarium oxysporum f. spp. However, hydrolytic enzymes like glucanase have not been detected in S. lydicus A02 on CMC-Na plates by congo red staining. Glucanase, a pathogenesis-related (PR) protein, degrades fungal cell walls and has been widely used as antifungal agent in plant protection. Therefore, a recombinant S. lydicus expressing a glucanase gene, which was cloned from the biocontrol strain Bacillus megaterium L103 and driven by the Streptomyces erythraea ermE* promoter, was constructed in this study. The engineered S. lydicus AG02 shared a similar yield of natamycin with the wild-type A02 strain. Compared to the wild-type strain A02, the engineered S. lydicus AG02 had a remarkably higher glucanase activity, as well as antifungal activity to F. oxysporum f. sp. conglutinans, F. oxysporum f. sp. niveum and Rhizoctonia cerealis. This demonstrated the improved biocontrol effect of S. lydicus AG02 attributed to transforming the exogenous glucanase from B. megaterium, which acted synergistically with natamycin to increase the antifungal activity of the strain.     

Octopine and nopaline synthesis and breakdown genetically controlled by a plasmid of Agrobacterium tumefaciens

Summary Several nopaline degrading strains and one octopine degrading strain are shown to loose oncogenicity as well as the ability to utilize these guanidine compounds when they are cured of their TI plasmid. To investigate whether the specific genes involved in the utilization of one or the other compound are located on the plasmid, plasmid-transfer experiments have been performed.The plasmid from a nopaline degrading strain has been transferred to a naturally non oncogenic Agrobacterium namely A. radiobacter. Furthermore, the plasmid from an octopine degrading strain has been transferred to a plasmid-cured strain which originally had the capacity to utilize nopaline. Both kinds of experiments prove that the TI plasmid determines the strain specificity with regard to the utilization of either octopine or nopaline.They also demonstrate that the synthesis of either octopine or nopaline in crown gall cells is also determined by genes located on the TI plasmid harboured by the transforming A. tumefaciens strains.     

Correlation between extracellular polysaccharide composition and nodulating ability inRhizobium trifolii

Summary Two auxotrophic mutants ofRhizobium trifolii which are deficient in nodulating ability have been isolated. Both mutants (strain RS 164 His^– and strain RS213 Leu^–) appear to synthesize abnormal extracellular polysaccharides as compared with the wild type strain RS 55. Simultaneous recovery of nodulating ability and wild type polysaccharide composition has been found in a Leu⁺ revertant of strain RS 213.Abbreviation EPS Extracellular Polysaccharide - NIG N-Methyl-N-Nitro-N-Nitrosoguanidine     

Histidine sensitive variant of the blue-green alga Nostoc muscorum: response to corepressors of histidine biosynthesis.

Summary A model has been proposed to account for growth inhibition by L-histidine in a variant strain of Nostoc muscorum. This strain has been characterized for its response to 3-amino-1,2,4-triazole and 1,2,4-triazole-3-alanine known to act as false corepressors of the histidine biosynthesis genes. The histidine sensitive strain retained its sensitivity to triazole alanine while the inhibitory effects of aminotriazole were much reduced indicating a change in regulation of his genes. The probable interactions between nif and his genes in cyanobacteria (blue-green algae) have been discussed.     

New haplotype and inter‐strain reproductive compatibility of Wolbachia‐uninfected alfalfa weevil,Hypera postica (Coleoptera: Curculionidae), in Japan

Hypera postica is a univoltine invasive pest of alfalfa, Medicago sativa, in North America. In Japan, H. postica was first found in 1982 from Fukuoka and Okinawa Prefectures and became a serious pest of Chinese milk vetch, Astragalus sinicus, cultivated as a honey source for humans and green manure for rice. In North America, three strains, Western, Eastern and Egyptian, have been identified and the Western strain is infected with Wolbachia, which causes complete inter‐strain reproductive incompatibility. In contrast, only Western and Egyptian strains had been reported throughout Japan and none of the Western strain examined for the Fukuoka populations in northern Kyushu was infected with Wolbachia. First, we screened populations from northern Kyushu collected since 1982 for geographical and chronological distribution of the Eastern strain. The Eastern strain has been found at low frequencies since 1985 and is still present in 2014. Second, we experimentally tested our hypothesis that inter‐strain crosses between uninfected Western‐strain males and Egyptian‐strain females should produce viable offspring. We crossbred virgin adults reared individually from field‐collected larvae and confirmed that the F₁ eggs of crosses between the Western‐strain males and the Egyptian‐strain females develop successfully into larvae.     

Degradation and bioconversion of aliphatic and aromatic hydrocarbons by Rhodococcus ruber 219

 A tetrahydrofuran-degrading bacterial strain, which had previously been tentatively assigned as Rhodococcus sp. strain 219, has now been identified as Rhodococcus ruber using physiological and chemotaxonomical tests. A comparison with the type strain DSM 43338 has revealed that the new strain differs in its ability to degrade or convert tetrahydrofuran and compounds of similar structure such as 2,5-dimethyltetrahydrofuran or tetrahydropyran. Tetrahydrofuran acts as an inducer for its degradation. When tetrahydrofuran-induced cells were incubated with 2,5-dimethyltetrahydrofuran two primary metabolites could be detected by gas chromatography, and 2-hydroxyhexane-5-one and hexane-2,5-dione were isolated and characterized by ¹H-NMR spectroscopy or as dinitrophenylhydrazones. The formation of these intermediates is consistent with an initial 2hydroxylation of the cyclic ether, which has not yet been described in microorganisms. Received: 19 July 1995/Received last revision: 31 October 1995/Accepted: 6 November 1995     

Reiterated DNA sequences in a mutant strain of Streptomyces glaucescens and cloning of the sequence in Escherichia coli

Summary Streptomyces glaucescens exhibits a high degree of genetic instability. A sequence of 7.2 kb has been found which is present in a few tandemly repeated copies in the wild type strain GLA 0 and is amplified to ca. 500 copies per genome in the mutant strain GLA 1204. This sequence was cloned in Escherichia coli using pBR325 as vector.     

An Escherichia coli mutant thermosensitive in the B subunit of DNA gyrase: effect on the structure and replication of the colicin E1 plasmid in vitro

Summary An E. coli strain which carries a mutation conferring clorobiocin resistance and temperature sensitivity for growth has recently been described and evidence has been presented suggesting that the mutation is located in the gyrB gene (Orr et al. 1979). The replication of the ColE1 plasmid was analysed in cell-free extracts from this thermosensitive strain. These extracts were totally deficient in the replication of exogenous plasmid DNA and were unable to maintain the superhelical structure of the plasmid DNA. Both defects could be fully complemented by addition of purified gyrB protein.     

Construction of a new strain of Streptomyces violaceoniger,having strong,constitutive and stable glucose-isomerase activity

Summary A newly isolated strong Streptomyces promoter (P1) has been cloned in front of the xylA gene of Streptomyces violaceoniger. This led to a strong and constitutive expression. To avoid instability of plasmid and glucose isomerase activity, the P1-xylA gene has been integrated into the chromosome using the integrative vector pTS55. The resultant CBS1 strain has about seven times higher glucose-isomerase activity in absence of xylose compared to that of wild type strain fully induced by xylose. In addition, glucose isomerase specific activity of the CBS1 strain increases in the secondary growth phase, in contrast to wild type strain.     

Degradation of Mineral Oil with a Strain of Acinetobacter calcoaceticus

The Acinetobacter calcoaceticusstrain TM-31 has been isolated from a microbial assemblage of a pilot plant that purifies waste water polluted with mineral oil. This strain is capable of efficient degradation of components of mineral oil (alkanes, isoalkanes, and alkyl residues of the naphthene and arene fraction). The strain bears stably inherited plasmids of sizes 120, 9, and 8 kb, which can be transferred into plasmid-free cells of the parental strain and into bacteria of the genusPseudomonasand ensure the degradation of hexadecane and mineral oil.     

Genetic studies on theH-3 region of mice and implications for polymorphism of histocompatibility loci

Evidence has been obtained for recombination betweenH-3 and the closely linkedIr-2 locus, which controls the antibody response toEa-1 antigens. The data suggest thatIr-2 maps close toH-3, betweenH-3 andH-13. The YBR strain has been found to possess anH-3 allele not previously reported. A comparison has been made between the degree of polymorphism of histocompatibility loci and that which involves electrophoretically detectable protein variants.     

Isolation of the <Emphasis Type="Italic">opdE</Emphasis> gene that encodes for a new hydrolase of <Emphasis Type="Italic">Enterobacter</Emphasis> sp. capable of degrading organophosphorus pesticides

Microbial enzymes that can hydrolyze organophosphorus compounds have been isolated, identified and characterized from different microbial species in order to use them in biodegradation of organophosphorus compounds. We isolated a bacterial strain Cons002 from an agricultural soil bacterial consortium, which can hydrolyze methyl-parathion (MP) and other organophosphate pesticides. HPLC analysis showed that strain Cons002 is capable of degrading pesticides MP, parathion and phorate. Pulsed-field gel electrophoresis and 16S rRNA amplification were performed for strain characterization and identification, respectively, showing that the strain Cons002 is related to the genus Enterobacter sp. which has a single chromosome of 4.6 Mb and has no plasmids. Genomic library was constructed from DNA of Enterobacter sp. Cons002. A gene called opdE (Organophosphate Degradation from E nterobacter) consists of 753 bp and encodes a protein of 25 kDa, which was isolated using activity methods. This gene opdE had no similarity to any genes reported to degrade organophosphates. When kanamycin-resistance cassette was placed in the gene opdE, hydrolase activity was suppressed and Enterobacter sp. Cons002 had no growth with MP as a nutrients source.     

Identification of the host-range DNA which allows Rhizobium leguminosarum strain TOM to nodulate cv. Afghanistan peas

Summary The special ability of Rhizobium leguminosarum strain TOM to nodulate cv. Afghanistan peas had previously been shown to be determined by the symbiotic plasmid, pRL5JI, of this strain. A region of pRL5JI, 2.0 kb in size, was found to confer the ability to nodulate cv. Afghanistan peas when transferred to strains of R. leguminosarum which normally fail to nodulate this host. This region of pRL5JI, responsible for the extension of host-range, was closely linked to, but did not include, the genes required for root hair curling. Although extensive homology has been found between the R. leguminosarum nod genes on pRL5JI and those on the normal symbiotic plasmid pRL1JI, a fragment from the 2.0 kb region involved in nodulation of cv. Afghanistan has been identified, which was not homologous to DNA in strains which do not nodulate cv. Afghanistan.     

Halobacterium salinarum strain MMD047-A low-salt adapted member of the Halobacteriaceae?

In a paper recently in Biotechnology and Bioprocess Engineering (vol. 14, pp. 67–75), Shanmughapriya and coworkers described a prokaryote (strain MMD047) isolated from a marine sponge, which they classified as a strain of Halobacterium salinarum. As the strain grows at low salinity only, its behavior is greatly different from that of other Halobacterium isolates. In spite of multiple requests, the strain has not been made available for further studies and we therefore call upon the authors of the paper to release their interesting isolate for an in-depth taxonomic characterization.     

Construction of Broad Host Range Cloning Vectors for Gram-negative Bacteria

A new cloning vector, pMFY31, has been constructed based on the high-copy-number, broad-host-range plasmid RSF1010. The plasmid has a size of 13.2 kb and carries the Ap^r, Cm^r, and Tc^r genes. It contains unique PstI, EcoRI, HindIII, BamHI, and SalI sites, all of which are located within the antibiotic resistance genes, therefore all sites are applicable to insertional inactivation. We also constructed pMFY40, a 11.6 kb derivative of pMFY31, by the elimination of the Cm^r gene. Plasmid pMFY31 has been efficiently introduced into a Pseudomonas putida strain not only by plasmid-DNA transformation but also by conjugal co-transfer with the helper plasmid, and was maintained stably in the strain.     

IS4 at its chromosomal site in E. coli K12

Summary IS4 DNA has been isolated in pure form. Hybridization of this DNA against restricted DNA of several E.coli K12 strains by Southern's blotting technique has shown that, in most strains, only one copy of IS4 is present. Though the restriction fragments around this site differ in size, IS4 can be shown always to be located at the same site. In one strain, one additional copy has been found in a new location. In this strain, IS4 in its original location has been retained.     

Isolation of bacterial consortia for degradation of p-nitrophenol from agricultural soil

bacterial consortium has been isolated containing Pseudomonas spp. strains S1 and S2, which was able to degrade p‐nitrophenol (PNP). The strains were isolated from agricultural soil contaminated with organophosphorus pesticides. Pseudomonas spp. strain S2 could convert p‐nitrophenol to 4‐nitrocatechol (4NC) after pre‐exposure to phenol, when PNP was used as the only carbon source in the medium. Pseudomonas spp. strain S2, when mixed with strain S1 in the ratio 1:5 respectively, decolorised PNP completely.