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We have amplified by PCR Pneumocystis carinii cytoplasmic small-subunit rRNA (variously referred to as 16S-like or 18S-like rRNA) genes from DNA extracted from bronchoalveolar lavage and induced sputum specimens from patients positive for P. carinii and from infected ferret lung tissue. The amplification products were cloned into pUC18, and individual clones were sequenced. Comparison of the determined sequences with each other and with published rat and partial human P. carinii small-subunit rRNA gene sequences reveals that, although all P. carinii small-subunit rRNAs are closely related (ϳ96% identity), small-subunit rRNA genes isolated from different host species (human, rat, and ferret) exhibit distinctive patterns of sequence variation. Two types of sequences were isolated from the infected ferret lung tissue, one as a predominant species and the other as a minor species. There was 96% identity between the two types. In situ hybridization of the infected ferret lung tissue with oligonucleotide probes specific for each type revealed that there were two distinct strains of P. carinii present in the ferret lung tissue. Unlike the ferret P. carinii isolates, the smallsubunit rRNA gene sequences from different human P. carinii isolates have greater than 99% identity and are distinct from all rat and ferret sequences so far inspected or reported in the literature. Southern blot hybridization analysis of PCR amplification products from several additional bronchoalveolar lavage or induced sputum specimens from P. carinii-infected patients, using a 32 P-labeled oligonucleotide probe specific for human P. carinii, also suggests that all of the human P. carinii isolates are identical. These findings indicate that human P. carinii isolates may represent a distinct species of P. carinii distinguishable from rat and ferret P. carinii on the basis of characterization of small-subunit rRNA gene sequences.

Candida albicans cells can survive and form biofilms in anaerobic and nutrient-limited conditions and may pose a treatment challenge.

The melon fly, Bactrocera cucurbitae (Coquillett), and the pumpkin fly, Bactrocera tau (Walker), are economically important pests that attack mainly cucurbitacean fruits. The two fruit fly species have similar natural distributions, host ranges, and population growth capacities. This study was designed to assess the asymmetrical competitions through resource exploitation between the larvae of B. cucurbitae and B. tau at different density levels and temperatures, and on different hosts by comparing the relative effects of interspecific and intraspecific interactions on four life history parameters: survival rate, puparial mass, puparial duration, and developmental duration. Our results showed that intraspecific and interspecific competitions occurred under some laboratory conditions, and B. cucurbitae took advantage over B. tau at the high-density level and at low and high temperatures on pumpkin, bitter gourd, and bottle gourd when interspecific competition took place. Intraspecific and interspecific competitions mainly affected the puparial mass and the survival rate of the two fruit fly species but had no marked effect on the puparial duration or development duration.