Isolation of Bacillus thuringiensis strains that contain Dipteran-specific cry genes from Ilha Bela (São Paulo, Brazil) soil samples.

The entomophatogenic bacterium Bacillus thuringiensis produces crystal proteins, named Cry proteins which are encoded by the cry genes. This bacterium is used on biological control of important economical pests, as well as in the control of disease´s vectors, such as Aedes aegypti, a mosquito that transmits the dengue viruses. Isolates of this bacterium can be characterized by the content of cry genes and this prediction helps target different insect orders. In this research, we isolated 76 colonies of B. thuringiensis from 30 soil samples that were taken from Ilha Bela (SP, Brazil), a place where simulids are already biologically controlled by B. thuringiensis, to find bacterial isolates that were capable of controlling A. aegypti. The 16S ribosomal subunit genes of the selected isolates were sequenced, and the isolates were molecularly characterized based on their Dipteran-specific cry gene contents. Eight of the 76 isolates (10.52%) contained the cry4Aa, cry4Ba or cry10Aa genes, these isolates were carried out against A. aegypti larvae on bioassay. The presence or absence of specific cry genes was associated with the observed average larval mortalities. From the 76 isolates, seven (9.2%) were potentially able to control A. aegypti larvae. Therefore these are promising isolates for the biological control of A. aegypti larvae.

Detecção de genes de resistência antimicrobiana em cromossomos e plasmídeos de staphylococcus spp

ABSTRACT The main of the present study was analyze the use of a french press device to obtain genetic material from staphylococci and to detect genes involved with chromosomal and plasmid resistance to the following antimicrobial drugs: oxacillin, gentamicin, kanamycin and vancomycin. The agar disc diffusion method was conducted initially for 50 strains and the bacterial susceptibility was confirmed by means of PCR reactions. The results from the antibiogram method revealed high sensibility to gentamicin and kanamycin (4%) and oxacillin (8%). All strains were susceptible to vancomycin. The DNA from the bacteria was obtained by means of physical lyses using a french press device. The genes mecA and aph3 IIIa were detected on the staphylococci chromosome and the gene aac(6)Ie + aph(2) was observed either in the chromosome and in the plasmid content of the staphylococci analyzed. Based on the obtained results one can conclude that the methodology used to extract the genomic genetic material using the french press device was efficient and allowed a simple method to detect by PCR and to locate by ultracentrifugation, the staphylococci antibiotic resistance genes.

RESUMO Este trabalho teve por objetivo analisar o uso da prensa francesa para se adquirir material genético de estafilococos e detectar possíveis genes de resistência cromossomais e plasmidiais aos antimicrobianos oxacilina, gentamicina, canamicina e vancomicina. O método da difusão de discos em ágar foi realizado, inicialmente, para 50 linhagens de estafilococos e a susceptibilidade antimicrobiana foi confirmada por meio de Reação em Cadeia da Polimerase (PCR). Os resultados obtidos pelo antibiograma constataram alta susceptibilidade para gentamicina e canamicina (4%) e oxacilina (8%). Todas as linhagens foram susceptíveis à vancomicina. O DNA bacteriano foi obtido por lise física a partir da prensa francesa. Os genes mecA e aph3IIIa foram detectados no cromossomo dos estafilococos e o gene aac(6) Ie + aph (2") foi observado tanto no cromossomo como no plasmidio destas bactérias. Pelos resultados pode-se concluir que a metodologia utilizada para a extração de DNA genômico, por meio da prensa francesa, foi barata e eficiente, pois possibilitou a detecção por PCR e a localização, por ultracentrifugação, de genes de resistência em estafilococos.