High prevalence of unusual genotypes of Toxoplasma gondii infection in pork meat samples from Erechim, Southern Brazil

Toxoplasmosis is the most common cause of infectious uveitis in Brazil, with a higher frequency in the South of the country. We have collected samples from porcine tongue and diaphragm obtained in both large and small abattoirs and used molecular biological technique to determine the prevalence of infection and RFLP analysis to type the parasites. Seventeen out of 50 (34%) samples from the diaphragm and 33 out of 50 (66%) samples from the tongue demonstrated a positive PCR reaction for T. gondii and restriction analysis of four of the positive samples revealed that all had a type I genotype at SAG2. However, when other unlinked loci were analyzed, these strains had a type III genotype at markers BTUB, SAG3, and GRA6. One of the strains (8T) had a type II allele at SAG3, indicating it has a combination of alleles normally seen in the clonal lineages. Our sampling indicates a high prevalence of infection and suggests that unusual genotypes of T. gondii are found in Brazil even among domesticated pigs.

Determination of the microbial diversity of anaerobic-aerobic activated sludge by a novel molecular biological technique

Sequential anaerobic-aerobic batch reactors were maintained on acetate/peptone and two different P/total organic carbon ratios that select for microbial communities enriched for either glycogen-accumulating organisms (GAO) or polyphosphate-accumulating organism (PAO). The community profiles of the eubacterial population and gram-positive high G-C bacteria (HGC) were characterized and compared by determining the terminal restriction fragment length polymorphisms (T-RFLP) of 16S rDNA. The HhaI+RsaI digested 5′ T-RFLP patterns of the eubacterial 16S rDNA amplified from the GAO- and PAO-enriched communities were made up with 12 and 14 rank-abundant fragments (i.e., ribotypes), respectively. Among those ribotypes detected in the GAO-enriched community, only seven were found in the PAO-enriched community. The HGC group could only account for no more than 6% and 17% of the eubacterial 16S rDNA amplified from the GAO- and PAO-enriched communities, respectively. Within the HGC community, at least 16 and 10 rank-abundant ribotypes were observed in the MspI digested T-RFLP patterns of GAO- and PAO-enriched communities, respectively. Among those HGC ribotypes observed in both communities, only five were in common. These indicate that the enrichment processes leading to the establishment of GAO- and PAO-specific communities caused the dramatic difference and complexity in the microbial population.

Multilocus DNA fingerprints in seven species of salmonids

DNA fingerprinting is a molecular biological technique that is widely used for identifying parentage and relatedness in plants and animals. To identify new DNA fingerprinting probes for use with salmonids, Southern blots of genomic DNA from chinook salmon (Oncorhynchus tshawytscha) were hybridized at low stringencies with 12 different oligonucleotides designed from published core sequences of variable number of tendem repeats. Seven of the 12 oligonucleotides produced highly variable fingerprint-like patterns; however, only 3 of these had clear, distinct bands. The estimated heterozygosity for one population of chinook salmon using the three oligonucleotides as probes ranged from 0.64 to 0.77. Those three oligonucleotides were further hybridized with DNA from two unrelated individuals from six other species of salmonids. A single-locus DNA fingerprint probe originally developed for chinook salmon was also hybridized with DNA from the other six species at moderate stringency. There were differences in the complexity and signal strength of the resulting banding pattern between species for a given probe. Estimates of variability (heterozygosity and band sharing) for the three oligonucleotide probes and OtSL1 were high, indicating that the probes were potentially useful genetic markers. The availability of these additional DNA fingerprint probes should assist in ecological and evolutionary studies in salmonids, as well as in efforts to estimate genetic diversity of populations.