Cloning and starch degradation profile of maltotriose-producing amylases from Streptomyces species
The end products from starch hydrolysis by amylases have important applications in various industries. Here, two amylases derived from two Streptomyces species that hydrolyze soluble starch from potato produced maltotriose as the primary maltooligosaccharide product. The genes, annotated as putative glycoside hydrolases, were cloned and expressed in Streptomyces lividans. These amylases displayed hydrolysis activity from pH 3 to 9.5 and were not affected by Ca2+. Optimal production of maltotriose was between 20 and 30 °C at pH 6.5. At the optimal temperature, both amylases produced maltotriose-rich end products rather than either maltose or maltotetraose.
Production and partial purification of α-amylase from a novel isolate Streptomyces gulbargensis
Extracellular amylase production by a newly isolated alkali-thermotolerant strain Streptomyces gulbargensis DAS 131 was optimized and characterized. The highest amylase production was achieved by growing S. gulbargensis DAS 131 in media with 1% starch. Strain exhibited maximal activity at pH 9.0 and 45°C and relatively stable in alkaline conditions (pH 11). Starch and peptone were found to be the good source of carbon and nitrogen with a yield of 2,216.6 and 2,156.1 U, respectively. Maltose and maltotriose were the main end products of starch hydrolysis, indicating α-amylase activity. SDS-PAGE analysis revealed a monomeric form with a molecular weight of 55 kDa.
Genotypic diversity in field isolates of Babesia bovis from cattle with babesiosis after vaccination.
OBJECTIVE
To determine whether particular genotypes of Babesia bovis were common to field isolates obtained from cattle properties in Queensland where the B bovis vaccine had apparently failed.


DESIGN
A comparative study of polymerase chain reaction genotypes in different populations of B bovis.


PROCEDURE
Two polymerase chain reaction assays were applied to analyse DNA extracts of B bovis vaccine (K, T and Dixie strains) and 27 field isolates from 24 properties where disease outbreaks had occurred despite the use of the vaccine. To evaluate the stability of the genotypes identified, 11 of the field isolates were inoculated into experimental cattle that had either been previously vaccinated with T strain or not vaccinated.


RESULTS
No particular genotype of B bovis was responsible for the problems observed in previously vaccinated herds. None of the isolates had genotypes identical to the vaccine strains used. No geographic trends among the genotypes were observed. Isolates that originated from the same property also had different genotypes. Blood passage of the 11 field isolates in either previously vaccinated or nonvaccinated cattle did not alter the original genotype.


CONCLUSION
No particular genotypes identified by the Bv80 and BvVA1 polymerase chain reaction assays could be associated with vaccine failures.