Benito Pereyra-Alférez

A Paecilomyces fumosoroseus mutant over-producing chitinase displays enhanced virulence against Bemisia tabaci

A Paecilomyces fumosoroseus strain was mutagenized by u.v. Among 200 colonies, one mutant (M84), showed a large and stable chitin hydrolysis-halo. Glucose consumption and biomass production were similar for M84 and the parental strain. Chitinase was inducible by chitin and repressed by glucose in both strains but, when they were grown on minimal medium plus colloidal chitin as sole carbon source, the parental and M84 strains yielded 198 and 690 μmol N-acetylglucosamine, respectively. This results indicate that the mutant strain synthesized a chitinase with a higher activity. Bioassays against Bemisia tabaci nymph, showed that M84 incited a 2-fold higher incidence of disease compared to the parental strain.

Bacteriocins synthesized by Bacillus thuringiensis: generalities and potential applications

The members of the Bacillus thuringiensis group, commonly known as Bt, produce a huge number of metabolites, which show biocidal and antagonistic activity. B. thuringiensis is widely known for synthesizing Cry, Vip and Cyt proteins, active against insects and other parasporins with biocidal activity against certain types of cancerous cells. Nevertheless, B. thuringiensis also synthesizes compounds with antimicrobial activity, especially bacteriocins. Some B. thuringiensis bacteriocins resemble lantibiotics and other small linear peptides (class IIa) from the lactic acid bacteria bacteriocins classification system. Although many bacteriocins produced by Bt have been reported, there is no proper classification for them. In this work, we have grouped these based on molecular weight and functionality. Bacteriocins are small peptides synthesized by bacteria, presenting inhibitory activity against Gram-positive and Gram-negative bacteria and to a lesser extent against fungi. These molecules represent a good study model in the search for microbial control alternatives. Lactic acid bacteria produces a huge number of these types of molecules with great potential. Nonetheless, members of the Bacillus, cereus group, especially B. thuringiensis, emerge as an attractive alternative for obtaining bacteriocins showing novel activities. This review describes the potential applications of B. thuringiensis bacteriocins in the control of foodborne pathogens, environment and medical area.

Genome annotation of a Saccharomyces sp. lager brewer's yeast.

The genome of lager brewers yeast is a hybrid, with Saccharomyces eubayanus and Saccharomyces cerevisiae as sub-genomes. Due to their specific use in the beer industry, relatively little information is available. The genome of brewing yeast was sequenced and annotated in this study. We obtained a genome size of 22.7 Mbp that consisted of 133 scaffolds, with 65 scaffolds larger than 10 kbp. With respect to the annotation, 9939 genes were obtained, and when they were submitted to a local alignment, we found that 53.93% of these genes corresponded to S. cerevisiae, while another 42.86% originated from S. eubayanus. Our results confirm that our strain is a hybrid of at least two different genomes.

Novel toxicity of native and HD Bacillus thuringiensis strains against to the sugarcane borer Diatraea saccharalis

Diatraea saccharalis (F.) (Lepidoptera: Pyralidae) is a pest that causes great economic losses to sugarcane producers in Mexico. In order to obtain alternatives for control of this pest, several Bacillus thuringiensis strains (native and from the Howard Dulmage collection) were tested. In bioassays, strains HD-133, HD-551, GM-7, GM-10, and GM-34 caused more than 50% mortality with a 50 μg/ml spore-crystal complex concentration, and were selected as toxic strains. The lowest LC50 value corresponded to GM-34 (33.21 μg/ml). Cry1B and cry1C genes were detected by PCR analysis in the toxic strains. HD-133 and GM-10 habored cry1C gene, HD-551 and GM-7 strains harbored cry1B gene, while GM34 strain did not contain cry1B nor cry1C. An additional PCR analysis was performed to detect cry1A-type genes. All the toxic strains habor at least one cry1A-type gene. Immunoblotting revealed that all strains cross-reacted with an antiCry1A, and only the HD-551 gave a positive signal with antiCry1B polyclonal antisera. GM-7 crystal protein showed no cross-reaction with polyclonal Cry1B antiserum. The toxicity of these strains may be related to some member of the Cry1A toxin class.

Genetic structure of Mexican Mestizos with type 2 diabetes mellitus based on three STR loci.

BACKGROUND The aims of this population genetics study were: 1) to ascertain whether Mexicans with type 2 diabetes mellitus (DM) were genetically homogeneous and 2) to compare the genetic structure of this selected population with the previously reported data of four random populations (Nuevo León, Hispanics, Chihuahua, and Central Region of Mexico). METHODS A sample of 103 unrelated individuals with DM and whose 4 grandparents were born in five zones of Mexico was interviewed in 32 Medical Units in the Mexican Institute of Social Security (IMSS). The non-coding STRs D16S539, D7S820, and D13S317 were analyzed. RESULTS Genotype distribution was in agreement with Hardy-Weinberg expectations for all three markers. Allele frequencies were found to be similar between the selected population and the four random populations. Gene diversity analysis suggested that more than 99.57% of the total gene diversity could be attributed to variation between individuals within the population and 0.43% between the populations. CONCLUSIONS According to the present and previous studies using molecular and non-molecular nuclear DNA markers not associated with any disease, the Mexican Mestizo population is found to be genetically homogeneous and therefore the genetic causes of DM are less heterogeneous, thereby simplifying genetic epidemiological studies as has been found in a previous study with the same design in Mexican women with breast cancer.

Evaluation of Heterorhabditis indica (Rhabditida: Heterorhabditidae) Nematode Strain from Sinaloa, Mexico, Against Bemisia tabaci Immatures Under Laboratory Conditions

Abstract. A native strain of Heterorhabditis indica Poinar, Karunakar & David nematode from Guasave, Sinaloa, Mexico, was identified by sequencing internal transcribed spacer regions of ribosomal DNA (rDNA). Assays against immature sweetpotato whitefly, Bemisia tabaci (Gennadius), used four strains of nematodes: Heterorhabditis bacteriophora Poinar Guatemala strain, H. bacteriophora Chiapas strain, a commercial product Steinernema feltiae (Filipjev) (Koppert®), and the H. indica native strain from Sinaloa. All strains at concentrations of 1,000, 750, 500, and 250 infective juveniles per milliliter, without significant differences among them, killed 70 to 95% of B. tabaci biotype B nymphs on leaves of tomato, Solanum lycopersicum (Mill), under laboratory conditions. This study is the first report of a native H. indica strain in Mexico, which is proposed as a biological control agent against B. tabaci.

Evidence of cross gene regulation of some virulence factors of Porphyromonas gingivalis by Streptococcus intermedius

Periodontal disease has been associated with poor dental care, which promotes the accumulation of bacteria and the development of diseases of the mouth. Porphyromonas gingivalis are anaerobic Gramnegative bacteria found in the subgingival plaque. They are largely responsible for chronic periodontal disease. Streptococcus intermedius is a Gram positive coccus found in the supragingival plaque. The objective of the present work was to evaluate the expression of several virulence genes of P. gingivalis in a mixed culture with S. intermedius using qPCR and heterologous microarrays. P. gingivalis ATCC 33277 and W83 and S. intermedius ATCC 27335 strains were cultured and total RNA was extracted using the High Pure RNA isolation kit. Oligodeoxynucleotides were designed to make multiple comparisons with organisms. Microarray was performed to identify gene expression. To quantify gene expression, cDNA samples from three different P. gingivalis:S. intermedius ratios were diluted 10-1, 10-2 and 10-3. The microarray experiment indicated that in P. gingivalis , 29 genes were upregulated. The putative function of upregulated genes was the biosynthesis of different metabolic pathways. Heterologous microarrays are a new approach that are useful for investigating gene expression. Keywords: Porphyromonas gingivalis, Streptococcus intermedius , periodontal disease, virulence genes, cross gene regulation. African Journal of Biotechnology Vol. 12(28), pp. 4498-4502

Detection of group I and group II introns in a Mexican Bacillus thuringiensis collection

Group I and II introns are non-coding sequences able to excise themselves from precursor mRNA by self-splicing. Both groups are ribozymes and may also code Open Reading Frames (ORF) for enzymes involved in the homing process; the Homing Endonuclease (HEase) in group I introns and maturase for group II. In this study, Mexican Bacillus thuringiensis strains belong to the Universidad Autonoma de Nuevo Leon collection were evaluated for the presence of these introns. For this propose, specific primers were designed for group I introns inserted in the ribonucleotide reductase operon and group II introns B.th.I, Bth.I2and B.th.I3. The PCR results obtained with primers for group I, was a DNA band of 600 bp for most strains (fifty four) and one of 200 bp for six one. The nucleotide sequence of 600 pb DNA band revealed more than 95% homology with the amplicons and group I introns reported before. Concern to group II introns, we can not see PCR products correspond to expect DNA band size.

Biosynthesis of amino acids sulfur in Saccharomyces cerevisiae is affected by fermentation conditions in beer production

Beer elaboration process is still considered, at least in part, an art. It is well known that both yeast and wort play an important role in the quality of final product, because several wort-compounds have influence in aroma and taste. In response to wort composition, the metabolic pathways can be modified in the yeast, and final product could result with high concentration of undesirable volatile sulfur compounds (VSC), mainly H2S and SO2. In this work we analyzed the expression of genes involved in the biosynthesis of VSC in Saccharomyces cerevisiae growing under different fermentation conditions. We designed two kinds of wort: one produced with high content of malt (above 50%) and other with low content of malt (below 50%), and were inoculated with yeast previously maintained at 4°C/4h and 18°C/18h, respectively. Yeast was collected at second day of fermentation and gene expression analysis was done using DNA microarrays. Biosynthesis pathway of sulfur amino acids was affected since the genes MUP3, HOM2, MET2, SER2 and MET3 were up regulated, while genes such as MET13, MET6 and MHT1 were down regulated. Moreover, H2S production was increased in low malt worts. Our results demonstrate that the wort composition plays an important role in the biosynthesis of sulfur amino acids and it could impact the generation of VSC.

Identification and characterization of a Cry7-like protein of Bacillus thuringiensis GM-33 strain holotype for subsp. monterrey

V.E. Aguirre-Arzola, A. G, Alcazar-Pizana, L. J. Galan-Wong, H. A. Luna-Olvera, B.E. Rivera Chavira and B. Pereyra-Alferez 1 Instituto de Biotecnologia. Facultad de Ciencias Biologicas. Universidad Autonoma de Nuevo Leon. Pedro de Alba y Manuel L. Barragan S/N. Cd. Universitaria. San Nicolas de los Garza, NL. 66450. Mexico 2 Facultad de Ciencias Quimicas. Universidad Autonoma de Chihuahua. Av. Universidad S/N. Cd. Universitaria. Chihuahua, Apdo. Postal 669. c.p.31170, Mexico.