Transfer and expression of a Streptomyces cholesterol oxidase gene in Streptococcus thermophilus

The recombinant plasmid pNCO937 (8.1 kbp) containing a Streptomyces sp. cholesterol oxidase gene was introduced into Streptococcus thermophilus by electrotransformation. Transformation frequency was 7.2 x 10(5) colony forming units/micrograms of DNA. The presence of the cholesterol oxidase gene in S. thermophilus was confirmed with Southern blot analysis using a biotinylated probe. Thin-layer chromatographic analysis showed the expression of the Streptomyces cholesterol oxidase gene resulting in the oxidation of cholesterol to 4-cholesten-3-one. S. thermophilus may be a suitable host for the expression of other genes regulating prokaryotic cholesterol metabolism.     

High-frequency transformation ofLactobacillus casei with plasmid pHY300PLK by electroporation

To optimize the conditions for transformation ofLactobacillus casei ATCC 27092 cells with plasmid pHY300PLK, a shuttle vector forEscherichia coli andBacillus subtilis, by electroporation, we investigated the effects of the electrical parameters (voltage and resistance), the concentration of plasmid DNA, the cell age and density, the electroporation buffer, and other factors. Under optimal conditions of 2.0 kV, 100 ohm, and 25F, a transformation efficiency as high as 1.4×10⁷ transformants per g of plasmid DNA was obtained, with a survival rate of about 50%.L. casei YIT 9021, one of the PL-1 phage mutants of the ATCC 27092 strain, was also transformed with the same plasmid under optimal conditions. The transformants were confirmed to harbor the same intact plasmid molecules by agarose gel electrophoretic analysis.     

Expression of Bacillus subtilis levanase gene in Lactobacilus plantarum and Lactobacillus casei

Two Lactobacillus-Escherichia coli shuttle vectors, harbouring the levanase gene from Bacillus subtilis under the control of its own promoter (pLPEW1) or behind the E.coli tac promoter (pESIEW2), were constructed. Lactobacillus plantarum showed the same growth characteristics on selective plates and in liquid media containing inulin, after transformation with either pLPEW1 or pESIEW2. L. plantarum transformed with pLPEW1 could be selected on inulin plates, indicating that levanase expression can be used as a food-grade selection system for Lactobacillus. Lactobacillus casei grew faster in inulin-containing medium than L. plantarum after transformation with pESIEW2, but did not grow when harbouring pLPEW1. Inulin-degrading activities of 90 mU/ml were found in culture medium of L. plantarum containing pLPEW1 or pESIEW2, and of 500 mU/ml in medium of L. casei (pESIEW2). Addition of 1 mMm isopropyl -d-thiogalactoside to the culture medium had no effect on growth and levanase expression in L. plantarum (pESIEW2) and L. casei (pESIEW2) strains. Levanase produced by L. casei (pESIEW2) has a size of 75 kDa and 72 kDa, corresponding to that of unprocessed and mature B. subtilis levanase, respectively, suggesting that the protein produced is recognized and processed by a signal peptidase.     

Probiotic Lactobacillus casei Expressing Human Lactoferrin Elevates Antibacterial Activity in the Gastrointestinal Tract

In this study, Lactobacillus casei was used to deliver and express human lactoferrin (hLF) to protect the host against bacterial infection. Full-length hLF cDNA was cloned into a Lactobacillus-specific plasmid to produce the L. casei transformants (rhLF/L. casei). Antimicrobial activity of recombinant hLF was examined in inhibition of bacteria growth in vitro. A mouse model was established to test in vivo antibacterial activity and protective effect of orally-administered probiotic L. casei transformant in the gastrointestinal tract. Trials were conducted in which animals were challenged with E. coli ATCC25922. E. coli colony numbers in duodenal fluid from the group fed with rhLF/L. casei were significantly lower than those of the group fed with wild-type L. casei or placebo (P < 0.01). Histopathological analyses of the small intestine, showed both decreased intestinal injury and increased villi length were observed in the mice fed with rhLF/L. casei as compared with the control groups (P < 0.01). Our results demonstrate that L. casei expressing hLF exhibited antibacterial activity both in in vitro and in vivo. It also provides a potentially large-scale production of hLF as applications for treatment of infections caused by clinically relevant pathogens.     

Complete Genome Sequence of Lactobacillus casei Zhang,a New Probiotic Strain Isolated from Traditional Homemade Koumiss in Inner Mongolia,China

Lactobacillus casei Zhang is a new probiotic bacterium isolated from koumiss collected in Inner Mongolia, China. Here, we report the main genome features of L. casei Zhang and the identification of several predicted proteins implicated in interactions with the host.Koumiss, a traditional drink made from mare''s milk by nomadic peoples in China and Mongolia, is believed to be beneficial in the cure of digestive diseases and a wide range of chronic diseases, including tuberculosis, bronchitis, and anemia (3). Lactobacillus casei Zhang is a novel probiotic strain identified by screening of lactic acid bacteria isolated from koumiss samples collected in Inner Mongolia, China, and exhibits high-level resistance to acid and bile stresses, as well as antibacterial, antioxidative, and immunomodulatory properties (6, 7, 11).A whole-genome shotgun strategy was used for sequencing of the genome of L. casei Zhang. pUC18 plasmid libraries with insertions of 1.5 to 2.5 kb and 4 to 6 kb were constructed (8). Gaps were closed by sequencing of PCR products. Base calling and sequence assembly were carried out using the Phred/Phrap/Consed software package (http://www.phrap.org/), and reads giving a total of 6.2-fold coverage were assembled with an error rate of <0.0001. Gene prediction and annotation were performed as described previously (10).The complete genome of L. casei Zhang consists of a 2,861,848-bp circular chromosome and a 36-kb plasmid. The average G+C content of the chromosome is 46.5%, while the plasmid has a lower G+C content (10). The L. casei Zhang genome contains 2,804 predicted coding sequences (CDSs), five rRNA operons, and 59 tRNAs. No functional prophages were identified, except for the previously described prophage remnant (9). Genes for 41 transposases were found in the genome, and this number was much lower than (only about 30%) those of transposase genes in L. casei ATCC 334 and BL23 (1, 4), suggesting that insertion element (IS)-mediated genome diversification was less frequent in L. casei Zhang.Comparative genome analysis revealed that the number of phosphotransferase system (PTS)-related proteins varied significantly in L. casei strains. Almost twice as many PTS components were found in L. casei Zhang and BL23 as in L. casei ATCC 334. In contrast to L. casei ATCC 334, L. casei Zhang was found to have 33 PTS components consisting of 11 complete substrate-specific enzyme II (EII) complexes encoded by six genomic islands. The G+C contents of the six islands ranged from 41 to 47%, similar to the average G+C content of the L. casei Zhang genome. In addition, most of the EII components in L. casei Zhang (81 of 96) were conserved in L. casei BL23, suggesting that a large-scale loss of PTSs occurred in L. casei ATCC 334 during its evolution. Conspicuous redundancy of chromosome-encoded PTSs in L. casei Zhang may offer benefits in the transport and use of a large panel of carbon sources.Genes encoding five putative mucus-binding proteins (LCAZH_0407, LCAZH_2292, LCAZH_2478, LCAZH_2398, and LCAZH_1427) and a cluster of genes encoding bacteriocin biosynthetic proteins (LCAZH_2341 to LCAZH_2348) nearly identical to those in L. casei ATCC 334 and BL23 were identified in L. casei Zhang and may provide this bacterium with some competitive advantages in the gastrointestinal environment (2, 5).In conclusion, the comparative analysis revealed the flexibility of L. casei Zhang in sugar utilization. In addition, some possible hints for its interactions with the host were identified. This genome sequence will be the basis for systematic studies into the mechanism for the probiotic properties of L. casei Zhang.     

Lipoxygenase inhibitor from Lactobacillus casei

An inhibitor of plant lipoxygenase from culture filtrates of Lactobacillus casei was purified by column chromatography and shown to be benzoic acid. The isolated benzoic acid had an IC₅₀ of 350 M against purified soybean lipoxygenase at pH 9. L. casei therefore may have the potential to be used as a preservative against the oxidation of unsaturated fatty acids, thereby preventing undesirable flavours in foods.     

Protoplast fusion between Lactobacillus casei and Lactobacillus acidophilus

Summary From the fusion between Lactobacillus casei and Lactobacillus acidophilus, 8 fusants were selected: Four were able to ferment maltose, lactose, galactose and mannose, but two had greater abilities of acid production than parents. Increased values of up to 7.6–8 % in -galactosidase activity were obtained from two when compared to that of L. acidophilus, whereas another 2 had activities of 800 and 548 nmol/mg protein/min comparable to that of L casei giving a value of 400 nmol/mg protein/min in phospho--galactosidase activity.     

Nature of the phytochrome effect on the binding of glycolate oxidase to peroxisomes in vitro

The attachment of glycolate oxidase to the peroxisomal fraction derived from etiolated barley leaves (Hordeum vulgare L. cr. Dvir) is affected by light. The effect of red irradiation is reversed by subsequent far-red irradiation, indicating the involvement of phytochrome. This phytochrome effect is assumed to be related to phytochrome binding. Indeed, prevention by filipin (1.2·10^-6 mol g^-1 f wt) or cholesterol of phytochrome binding to membranes abolishes the effect of light on the interaction between glycolate oxidase and the peroxisomal fraction. Glycolate oxidase binding is affected by addition of quasi-ionophores such as gramicidin and filipin at a concentration of 0.6·10^-3 mol g^-1 f wt. This fact indicates that peroxisome-glycolate oxidase interaction may be affected by membrane potential. Since both ion transport and membrane potential are known to be affected by phytochrome, it is proposed that phytochrome acts in the light-induced modulation of glycolate oxidase attachment as a quasi-ionophore.Abbreviations GO glycolate oxidase - Pr and Pfr phytochrome forms absorbing in red and far-red, respectively - R and F red and far-red irradiation - Cumulative 20 Kp 20,000 g pellet obtained by centrifugation of the crude extract - 1 Kp 1,000 g pellet - 20 Kp 20,000 g pellet, obtained by centrifugation of 1 Kp supernatant - 1 Kp, 20 Kp and cumulative 20 Kp pellets obtained after density centrifugation through a sucrose cushion     

Relationship of vector insert size to homologous integration during transformation of Neurospora crassa with the cloned am (GDH) gene

Summary We used lambda and plasmid vectors containing the am ⁺ gene in an insert of from 2.7 to 9.1 kb, to transform am point mutant and deletion strains. A total of 199 transformants were examined with the potential to yield am ^– transformants by homologous recombination. When we used vectors that had 9.1 kb of homology with the chromosomal DNA, 30% of the transformants obtained were the result of homologous recombination regardless of whether the vector was a lambda molecule, a circular plasmid, or a plasmid that had been linearized prior to transformation. When vectors with up to 5.1 kb of homology were used, very few transformants (1 of 89 tested) resulted from homologous recombination. Of a sample of 29 ectopic integration events obtained by transformation with the 9.1 kb fragment cloned in a vector, 18 included a major part (usually almost all) of both arms of lambda with the entire Neurospora 9.1 kb insert between them. Four included only long arm sequence together with an adjacent segment of the insert containing the am gene. The remaining seven were the result of multiple integrations. There was no evidence of circularization of the vector prior to integration. All transformants that had multiple copies of the am gene appeared to be subject to the RIP process, which causes multiple mutations in duplicated sequences during the sexual cycle.     

Nisin‐induced expression of pediocin in dairy lactic acid bacteria

Aims: To test whether a single vector, nisin‐controlled expression (NICE) system could be used to regulate expression of the pediocin operon in Streptococcus thermophilus, Lactococcus lactis subsp. lactis and Lactobacillus casei. Methods and Results: The intact pediocin operon was cloned immediately into pMSP3535 downstream of the nisA promoter (PnisA). The resulting vector, pRSNPed, was electrotransformed into Strep. thermophilus ST128, L. lactis subsp. lactis ML3 and Lact. casei C2. Presence of the intact vector was confirmed by PCR, resulting in the amplification of a 0·8‐kb DNA fragment, and inhibition zones were observed for all lactic acid bacteria (LAB) transformants following induction with 50 ng ml^?1 nisin, when Listeria monocytogenes Scott A was used as the target bacterium. Using L. monocytogenes NR30 as target, the L. lactis transformants produced hazy zones of inhibition, while the Lact. casei transformants produced clear zones of inhibition. Zones of inhibition were not observed when the Strep. thermophilus transformants were tested against NR30. Conclusions: The LAB hosts were able to produce enough pediocin to inhibit the growth of L. monocytogenes Scott A; the growth of L. monocytogenes NR30 was effectively inhibited only by the Lact. casei transformants. Significance and Impact of the Study: This is the first time that the NICE system has been used to express the intact pediocin operon in these LAB hosts. This system could allow for the in situ production of pediocin in fermented dairy foods supplemented with nisin to prevent listeria contamination.     

Development of a genetic transformation system for Histoplasma capsulatum: complementation of uracil auxotrophy

Summary We have developed a simple and efficient transformation system for the dimorphic fungus Histoplasma capsulatum. Mutants of H. capsulatum defective in orotidine-5-monophosphate pyrophosphorylase were transformed to prototrophy by the cloned URA5 gene of the filamentous fungus Podospora anserina. Abortive and mitotically stable transformants were obtained. The stable transformants had integrated copies of the plasmid, some in tandem head-to-tail orientation. Free plasmid identical to the transforming plasmid was present in some of the transformants. We obtained a transformation efficiency of up to 30 transformants/g DNA for plasmid pPAura5-1 (9.2 kb). pPW2001, a smaller plasmid (4.7 kb) derived from pPAura5-1, transformed H. capsulatum more efficiently (up to 155 transformants/gm DNA).     

Gene inactivation in the plant pathogen Glomerella cingulata: three strategies for the disruption of the pectin lyase gene pnIA

The feasibility of performing routine transformation-mediated mutagenesis in Glomerella cingulata was analysed by adopting three one-step gene disruption strategies targeted at the pectin lyase gene pnIA. The efficiencies of disruption following transformation with gene replacement- or gene truncation-disruption vectors were compared. To effect replacement-disruption, G. cingulata was transformed with a vector carrying DNA from the pnlA locus in which the majority of the coding sequence had been replaced by the gene for hygromycin B resistance. Two of the five transformants investigated contained an inactivated pnlA gene (pnlA ^– );both also contained ectopically integrated vector sequences. The efficacy of gene disruption by transformation with two gene truncation-disruption vectors was also assessed. Both vectors carried a 5and 3truncated copy of the pnlA coding sequence, adjacent to the gene for hygromycin B resistance. The promoter sequences controlling the selectable marker differed in the two vectors. In one vector the homologous G. cingulata gpdA promoter controlled hygromycin B phosphotransferase expression (homologous truncation vector), whereas in the second vector promoter elements were from the Aspergillus nidulans gpdA gene (heterologous truncation vector). Following transformation with the homologous truncation vector, nine transformants were analysed by Southern hybridisation; no transformants contained a disrupted pnlA gene. Of nineteen heterologous truncation vector transformants, three contained a disrupted pnlA gene; Southern analysis revealed single integrations of vector sequence at pnlA in two of these transformants. pnlA mRNA was not detected by Northern hybridisation in pnlA-transformants. pnlA-transformants failed to produce a PNLA protein with a pI identical to one normally detected in wild-type isolates by silver and activity staining of isoelectric focussing gels. Pathogenesis on Capsicum and apple was unaffected by disruption of the pnlA gene, indicating that the corresponding gene product, PNLA, is not essential for pathogenicity. Gene disruption is a feasible method for selectively mutating defined loci in G. cingulata for functional analysis of the corresponding gene products.     

The impact of heterologous catalase expression and superoxide dismutase overexpression on enhancing the oxidative resistance in <Emphasis Type="Italic">Lactobacillus casei</Emphasis>

Two heme-dependent catalase genes were amplified from genomic DNA of Lactobacillus plantarum WCFS1 (KatE1) and Lactobacillus brevis ATCC 367 (KatE2), respectively, and a manganese-containing superoxide dismutase from Lactobacillus casei MCJΔ1 (MnSOD) were cloned into plasmid pELX1, yielding pELX1-KatE1, pELX1-KatE2 and pELX1-MnSOD, then the recombinant plasmids were transferred into L. casei MCJΔ1. The strains of L. casei MCJΔ1/pELX1-KatE1 and L. casei MCJΔ1/pELX1-KatE2 were tolerant at 2 mM H₂O₂. The survival rates of L. casei MCJΔ1/pELX1-KatE1 and L. casei MCJΔ1/pELX1-KatE2 were 270-fold and 300-fold higher than that of the control strain on a short-term H₂O₂ exposure, and in aerated condition, the survival cells counts were 146- and 190-fold higher than that of the control strain after 96 h of incubation. Furthermore, L. casei MCJΔ1/pELX1-MnSOD was the best in three recombinants which was superior in the living cell viability during storage when co-storage with Lactobacillus delbrueckii subsp. lactis LBCH-1.     

Biolistic transformation of tobacco and maize suspension cells using bacterial cells as microprojectiles

Summary We have used both Escherichia coli cells and Agrobacterium tumefaciens cells as microprojectiles to deliver DNA into suspension-cultured tobacco (Nicotiana tabacum L. line NT1) cells using a helium powered biolistic device. In addition, E. coli cells were used as microprojectiles for the transformation of suspension-cultured maize (Zea mays cv. Black Mexican Sweet) cells. Pretreating the bacterial cells with phenol at a concentration of 1.0%, and combining the bacterial cells with tungsten particles increased the rates of transformation. In N. tabacum, we obtained hundreds of transient transformants per bombardment, but were unable to recover any stable transformants. In Z. mays we obtained thousands of transient transformants and an average of six stable transformants per bombardment. This difference is discussed.Abbreviations BMS Black Mexican Sweet - RPM revolutions per minute - uidA -glucuronidase gene - GUS -glucuronidase protein - LB Luria-Bertani broth - OD600 optical density at 600 nm - psi pounds per square inch - Ap^r ampicillin resistance - Kn^r kanamycinresistance     

Nitrobacter winogradskyi cytochrome c oxidase genes are organized in a repeated gene cluster

Cytochrome c oxidase (EC 1.9.3.1) is one of the components of the electron transport chain by which Nitrobacter, a facultative lithoautotrophic bacterium, recovers energy from nitrite oxidation. The genes encoding the two catalytic core subunits of the enzyme were isolated from a Nitrobacter winogradskyi gene library. Sequencing of one of the 14 cloned DNA segments revealed that the subunit genes are side by side in an operon-like cluster. Remarkably the cluster appears to be present in at least two copies per genome. It extends over a 5–6 kb length including, besides the catalytic core subunit genes, other cytochrome oxidase related genes, especially a heme O synthase gene. Noteworthy is the new kind of gene order identified within the cluster. Deduced sequences for the cytochrome oxidase subunits and for the heme O synthase look closest to their counterparts in other -subdivision Proteobacteria, particularly the Rhizobiaceae. This confirms the phylogenetic relationships established only upon 16S rRNA data. Furthermore, interesting similarities exist between N. winogradskyi and mitochondrial cytochrome oxidase subunits while the heme O synthase sequence gives some new insights about the other similar published -subdivision proteobacterial sequences.Abbreviations COI cytochrome oxidase subunit I - COII cytochrome oxidase subunit II - COIII cytochrome oxidase subunit III - HOS Heme O synthase - ORF open reading frame - SDS sodium dodecyl sulfate     

Construction of a designer chromosome in tobacco

The tobacco (Nicotiana tabacum L.) breeding line NC 152 is a doubled haploid that possesses an addition chromosome from N. africana [Merxm. and Buttler]. A gene on this chromosome confers potyvirus resistance (Poty^R). Our objective was to use the addition chromosome as a base on which to construct a designer chromosome containing a foreign gene linkage package. A mutant dhfr gene conferring resistance to methotrexate (Mtx) was inserted into NC 152-haploid (n = 25) leaf tissue via Agrobacterium tumefaciens-mediated transformation. After chromosome doubling, 135 NC 152dhfr transformants (2n = 50) were pollinated with the potyvirus-susceptible (Poty^S) cultivar McNair 944 (2n = 48). Linkage analysis was performed in the BC₁ generation. Two transformants, NC 152dhfr-996 and NC 152dhfr-1517 exhibited complete linkage between Mtx resistance (Mtx^R) and Poty^R. Segregants from these two transformants which were Mtx^R and Poty^R possessed 49 chromosomes, while Mtx sensitive (Mtx^S) and Poty^S progeny possessed 48 chromosomes. Eighty percent of the NC 152dhfr transformants transmitted the dhfr gene as one locus. Other foreign genes can be directed to the addition chromosome through transformation followed by selection for single loci with linkage to Poty^R or Mtx^R. The integrity of both the foreign-gene linkage package and the rest of the genome will be maintained because recombination between the N. africiana and the N. tabacum chromosomes has not been observed.     

Human papillomavirus type 16 E6-specific antitumor immunity is induced by oral administration of HPV16 E6-expressing Lactobacillus casei in C57BL/6 mice

Given that local cell-mediated immunity (CMI) against the human papillomavirus type 16 E6 (HPV16 E6) protein is important for eradication of HPV16 E6-expressing cancer cells in the cervical mucosa, the HPV16 E6 protein may be a target for the mucosal immunotherapy of cervical cancer. Here, we expressed the HPV16 E6 antigen on Lactobacillus casei (L. casei) and investigated E6-specific CMI following oral administration of the L. casei-PgsA-E6 to mice. Surface expression of HPV16 E6 antigens was confirmed and mice were orally inoculated with the L. casei-PgsA or the L. casei-PgsA-E6. Compared to the L. casei-PgsA-treated mice, significantly higher levels of serum IgG and mucosal IgA were observed in L. casei-PgsA-E6-immunized mice; these differences were significantly enhanced after boost. Consistent with this, systemic and local CMI were significantly increased after the boost, as shown by increased counts of IFN-γ-secreting cells in splenocytes, mesenteric lymph nodes (MLN), and vaginal samples. Furthermore, in the TC-1 tumor model, animals receiving the orally administered L. casei-PgsA-E6 showed reduced tumor size and increased survival rate versus mice receiving control (L. casei-PgsA) immunization. We also found that L. casei-PgsA-E6-induced antitumor effect was decreased by in vivo depletion of CD4⁺ or CD8⁺ T cells. Collectively, these results indicate that the oral administration of lactobacilli bearing the surface-displayed E6 protein induces T cell-mediated cellular immunity and antitumor effects in mice.