Transforming ability of a T4 RNA-DNA copolymer.

A coliphage T4-specific RNA-DNA copolymer is genetically competent to transform a marker in gene 43, the DNA polymerase.

Variable transforming activity of nonglucosylated and fragmented T4 DNA.

Nonglucosylated and fragmented T4 DNA shows a gene-specific variation in transformation efficiency.

Biological activity of T4 DNA synthesized in toluene-treated Escherichia coli cells.

T4 DNA synthesized in a toluene-treated cell system can act as the genetic donor in a DNA transformation assay. This material transforms a variety of markers at high efficiency. We present evidence that the genetic activity is due to newly synthesized, double-stranded DNA.

Isolation and characterization of spontaneously arising auxotrophic and Kanagawa phenomenon-negative mutants of Vibrio parahaemolyticus.

As a first step toward developing a system of genetic exchange between Vibrio parahaemolyticus strains, spontaneously arising auxotrophic and Kanagawa phenomenon-negative (KP-) mutants were isolated and characterized. Auxotrophic mutants were selected by nalidixic acid enrichment of parental cultures. Some Cys- and Arg- mutants of a KP+ strain were found to be KP-. Reversion to prototrophy by these strains was not accompanied by a return to the parental KP+ phenotype. Additionally, two prototrophic KP- mutants were isolated. No detectable levels of vibriolysin were found in supernatant extracts of KP- mutants by slide gel immunodiffusion analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, or assay for lethal activity in mice. All Cys-, Arg-, and Pur- mutants tested reverted to a different auxotrophy (phenotypic interconversion) as well as to prototrophy. The possible role of insertion sequence-like elements in vibriolysin production and phenotypic interconversion is discussed.

Serology and plasmid carriage in Vibrio cholerae.

Vibrio cholerae strains of the 01 serovar, isolated from both clinical and environmental sources, had a much lower frequency of plasmid carriage (2/112 = 2%) than clinical and environmental non-01 serovar isolates (46/187 = 25%). The cryptic plasmids found in non-01 strains were all of low molecular weight and were shown by hybridization analysis to consist of two unrelated subgroups. Each subgroup was observed to be present in strains isolated from both clinical and environmental sources. One 01 serovar (ATCC 14033) carried a small cryptic plasmid, belonging to one of these plasmid groups, while a second (25728) contained a high molecular weight multiple antibiotic resistance plasmid which did not hybridize to either plasmid subgroup.

R-factor carriage in a group F vibrio isolated from Bangladesh.

Two group F vibrio organisms have been identified among a collection of vibrio strains isolated from the aquatic environment in Bangladesh. Neither group F strain produced a cholera-like enterotoxin. One of the isolates, BV12, contained an R plasmid conferring resistance to streptomycin and chloramphenicol.

Numerical taxonomy of Vibrio cholerae and related species isolated from areas that are endemic and nonendemic for cholera.

A total of 165 strains of vibrios isolated from clinical and environmental sources in the United States, India, and Bangladesh, 11 reference cultures, and 4 duplicated cultures were compared in a numerical taxonomic study using 83 unit characters. Similarity between strains was computed by using the simple matching coefficient and the Jaccard coefficient. Strains were clustered by unweighted average linkage and single linkage algorithms. All methods gave similar cluster compositions. The estimated probability of error in the study was obtained from a comparison of the results of duplicated strains and was within acceptable limits. A total of 174 of the 180 organisms studied were divided into eight major clusters. Two clusters were identified as Vibrio cholerae, one as Vibrio mimicus, one as Vibrio parahaemolyticus, three as Vibrio species, and one as Aeromonas hydrophila. The V. mimicus cluster could be further divided into two subclusters, and the major V. cholerae group could be split into seven minor subclusters. Phenotypic traits routinely used to identify clinical isolates of V. cholerae can be used to identify environmental V. cholerae isolates. No distinction was found between strains of V. cholerae isolated from regions endemic for cholera and strains from nonendemic regions.

A Plasmodium falciparum antigen containing clusters of asparagine residues.

A genomic DNA fragment that encodes a Plasmodium falciparum antigen has been isolated by using human antibodies eluted from the membrane of infected erythrocytes. The antigen has a very unusual primary structure; it is exceptionally rich in asparagine residues, many of which are distributed in clusters (2-15 residues) along the polypeptide chain. Unlike many P. falciparum antigens, this protein lacks tandemly repeated sequences. The antigen is distinct from Pf 155, a merozoite-derived antigen deposited in the membrane of infected erythrocytes, but contains epitopes that crossreact with anti-Pf 155 antibodies. Antisera prepared in mice against the asparagine-rich protein react with late-stage parasites in indirect immunofluorescence. In an in vitro merozoite reinvasion assay, the IgG fraction of a mouse polyclonal antiserum, as well as a mouse monoclonal antibody, gave significant inhibition. Three polypeptides (Mr 36,000, 30,000, and 15,000) were recognized by these antibodies on immunoblots of P. falciparum extracts.

Isolation of drug-resistant Aeromonas hydrophila from aquatic environments.

Antibiotic-resistant strains of Aeromonas hydrophila have been isolated from the natural environment in the Chesapeake Bay and areas surrounding Dacca and the Matlab region of Bangladesh. The Bangladesh strains carried resistance to chloramphenicol, streptomycin, and tetracycline, and 57% of them had a multiple streptomycin-tetracycline resistance phenotype correlated with the presence of a large plasmid. The Chesapeake Bay strains were resistant to polymyxin B ane tetracycline, but showed neither multiple resistance nor R-factor carriage. Twenty-five percent of the environmental strains were toxigenic in a Y-1 adrenal cell assay. Toxigenicity showed no positive correlation with drug resistance or with plasmid carriage. Environmental areas of heavy human impact appear to be associated with a higher incidence of antibiotic-resistant strains of aeromonads.