The postmodern turn in group therapy.

The postmodern critique, often referred to as social constructionism, has influenced nearly all disciplines, including recently the domain of psychology--and most particularly psychoanalysis. This article presents an exposition of the "postmodern turn," including some historical perspective, a description of its theoretical elements as related to psychological practice, as well as standard objections to its theories. This author believes that many of the concepts inherent to a social constructionist approach are compelling for theory and practice in group therapy. Clinical case studies are cited in describing how postmodern theories present a natural fit for group therapy. Furthermore, specific implications of this model are delineated for the arduous task of leading groups.

Novel Alterations in Plasmid DNA Associated with Aromatic Hydrocarbon Utilization by Pseudomonas putida R5-3.

Subcultures of Pseudomonas putida R5-3 altered their plasmid DNA content in specific ways depending on the particular aromatic hydrocarbon utilized as the sole carbon source. Two indigenous plasmids, 115 and 95 kilobases (kb) in size, were observed in R5-3A, which was derived from R5-3 by growth on minimal medium containing p-methylbenzoate as the sole carbon source. When R5-3A was transferred to medium containing m-xylene or toluene, derivative strains were obtained in which the 95-kb plasmid was lost and a new plasmid of 50 or 60 kb appeared. Reversion to the original plasmid profile of R5-3A was observed when xylene- or toluene-grown cells were returned to medium containing p-methylbenzoate. Restriction enzyme analysis and Southern blot hybridizations of total plasmid DNA indicated deletions and rearrangements of DNA restriction fragments in the derivatives maintained on m-xylene and toluene when compared with the original R5-3A. In the derivatives which retrieved the original plasmid profile, the restriction enzyme fragment pattern was identical to that in the original R5-3A, in that the fragments which were missing after growth on m-xylene or toluene were again present. Southern blot hybridizations revealed that part of the plasmid DNA lost from the original plasmid profile was integrated into the chromosomal DNA of xylene-grown R5-3B and that these plasmid fragments were associated with aromatic hydrocarbon metabolism. Hybridization with pathway-specific DNA fragments from the TOL plasmid pWWO indicated that this 95-kb plasmid contains DNA homologous to the meta-fission pathway genes.

Identification of Pseudomonas alcaligenes chromosomal DNA in the plasmid DNA of the chlorobenzene-degrading recombinant Pseudomonas putida strain CB1-9.

The recombinant Pseudomonas putida strain CB1-9, which acquired the ability to grow on chlorobenzenes, contains a 33-kilobase (kb) plasmid (pKFL3) which lacked homology to an indigenous 15-kb plasmid (pKFL1) in Pseudomonas alcaligenes C-0 parent but was homologous to a 55-kb plasmid (pKFL2) from the P. putida R5-3 parent. Chromosomal DNA of P. alcaligenes C-0 hybridized to probes prepared from pKFL3 but not to probes prepared from pKFL2. A single clone from a genomic library of P. alcaligenes C-0 hybridized to EcoRI-digested pKFL3. Southern blot hybridization with the insert DNA from that clone identified homology with specific restriction enzyme fragments in pKFL3. The ability of the recombinant to utilize 3-chlorobenzoate, chlorobenzene, and 1,4-dichlorobenzene as well as its loss of utilization of xylenes and methylbenzoates appears to be associated with the transfer and integration of chromosomal DNA from P. alcaligenes into a Tol-like plasmid of P. putida R5-3.

Isolation of Pathogenic Bacillus circulans from Callus Cultures and Healthy Offshoots of Date Palm (Phoenix dactylifera L.).

Pure cultures of a gram-negative, rod-shaped bacterium, which produced endospores after 3 to 5 days on solid medium, were isolated exclusively from tissue cultures of the date palm Phoenix dactylifera L. Electron microscopic examination of thin sections of the bacteria revealed the bilayer membrane typical of gramnegative bacteria and confirmed the nature of the spores as true endospores. Biochemical and physiological tests indicated that the bacteria were Bacillus circulans. B. circulans was consistently isolated from the internal tissues, including the meristem, of apparently healthy offshoots of date palm. When meristem and embryo callus tissue culture samples were injected with B. circulans isolated from similar tissue culture samples and from offshoots, the majority of the isolates produced a rapid, destructive soft rot of the tissues.

Conjugal transfer of E. coli F'lac from Erwinia chrysanthemi to Pseudomonas syringae pv. glycinea and the apparent stable incorporation of the plasmid into the pv. glycinea chromosome.

The E. coli F'lac plasmid was transferred from an Erwinia chrysanthemi Hfr8 donor to a multiply-auxotrophic, rifampicin-resistant Pseudomonas syringae pv. glycinea recipient. Transfer occurred at a frequency of approximately 10(-5)/donor. Stable transconjugants which were able to utilize lactose as the sole carbon source after several transfers would not donate the F'lac plasmid in detectable frequency to other pv. glycinea or E. coli recipients. The plasmid DNA was shown to be integrated into the pv. glycinea chromosome (Fig. 1).

The mutagenicity of natural products from marine algae.

5 polyhalogenated hydrocarbon natural products isolated from the marine red alga Plocamium spp. were tested for mutagenicity in the Ames reversion assay. All 5 of the compounds induced revertants in Salmonella typhimurium strains TA100 and TA1535, indicating the mutational events involved base substitutions. One of the compounds, designated cross-conjugated ketone, was shown to be almost 200 times more effective as a mutagen than was ethyl methanesulfonate.

Transfer and integration of chromosomal genes from Pseudomonas glycinea into Pseudomonas aeruginosa.

The plasmids FP2 and R68.45 were shown to function as chromosome-mobilizing plasmids in a series of interspecific crosses between the phytopathogen Pseudomonas glycinea and the human pathogen Pseudomonas aeruginosa. At least four of seven loci tested were transferred from P. glycinea donors to P. aeruginosa auxotrophic recipients. Transductional analysis indicates that a leu+ locus of the P. glycinea chromosome transferred is stably integrated into the P. aeruginosa chromosome.

Linkage analysis of Pseudomonas glycinea.

The IncP-1 plasmid R68 and variants R68.45 and R68.185 were tested for their chromosome donor ability in a selected recipient of Pseudomonas glycinea PGR12. It was found that variants did not express their selected characteristic of increased donor ability over that of R68 or R68.5, our commonly used donor plasmids. Coinheritance analysis of a variety of crosses provides evidence of a linkage group comprising 11 loci.

Heterokaryosis in Fusarium oxysporum f.sp. lycopersici.

Intra-isolate and inter-isolate heterokaryons were synthesized between auxotrophic mutants of Fusarium crown rot, 'purple variant' and the wilt isolates. This is the first report of intra- and inter-isolate heterokaryons in Fusarium oxysporum f.sp. lycopersici. Conidial ratios determined for several heterokaryons between different mutants of the Fusarium crown rot organism showed that the ratio is constant for each heterokaryon and that the ratio usually is in favour of one of the mutants.

Transfer of antibiotic resistance plasmid RP1 into Pseudomonas glycinea and Pseudomonas phaseolicola in vitro and in planta.

The wide host-range antibiotic resistance plasmid RP1 was transferred from Pseudomonas aeruginosa via Escherichia coli into Pseudomonas glycinea. The plasmid was then acquired by Pseudomonas phaseolicla both in vitro and in planta in Phaseolus limensis leaves and pods. This was the first step in the design of a model system to determine the possible epidemiological significance of antibiotic resistance plasmids in the control of plant disease.

Chemical mutagenesis of Fusarium oxysporum f. sp. lycopersici: non-selected changes in pathogenicity of auxotrophic mutants.

Single and multiple auxotrophic mutants of the Fusarium oxysporum f. sp.lycopersici strains which cause Fusarium crown-rot and Fusarium wilt of tomato were obtained by chemical mutagenesis with nitrous acid, nitrosoguandidine and ethylmethaneulphonate. The mutagenesis and selection procedures, adapted for use with a plant pathogenic fungus, are described. Changes in pathogenicity were observed when the auxotrophs were compared with the wild type but no correlation was observed between changes in pathogenicity and the particular nutritional requirement.

Antimicrobial agents from marine algae.

The antimicrobial activity of five compounds extracted from marine algae was tested against Staphylococcus aureus, Salmonella choleraesuis, Mycobacterium smegmatis, Candida albicans, and Escherichia coli. Three of the compounds, cycloeudesmol, laurinterol, and debromolaurinterol, exhibited activity at concentrations approaching that of streptomycin. None of the compounds inhibited all of the organisms tested. There appeared to be selectivity for gram-positive microbes.