Photoreactivation of Pseudomonas cepacia after ultraviolet exposure: a potential source of contamination in ultraviolet-treated waters

Cells of a naturally occurring strain of Pseudomonas cepacia grown in distilled water were exposed to ultraviolet radiation. Irradiated samples incubated on membrane filters or in fluid recovery media in the absence of light showed no evidence of dark repair mechanisms. When samples were exposed to fluorescent light ranging from 50 to 950 foot candles (538 to 10,222 lux) of illumination, apparent photo-induced repair of ultraviolet injury resulted in 1- to 4-log increases in viable cells recovered.

Camphor plasmid-mediated chromosomal transfer in Pseudomonas putida

Camphor-utilizing strains of Pseudomonas putida have been shown to carry the genetic information required for camphor degradation on a plasmid. The plasmid-carrying strains can serve as donors of both plasmid-borne and chromosomal genes. As recipients, plasmid-deleted strains are much superior to those carrying the camphor pathway genes. The transfer frequency of chromosomal, but not plasmid-borne, genes is markedly enhanced if the donor cells are irradiated with ultraviolet light followed by 3-h of growth on a rich medium in the dark. Recombinants selected for prototrophy are stable and most acquire the camphor (CAM) plasmid concomitantly; only a few of the Cam(+) recombinants inherit the donor's ability to transfer chromosomal genes at a high frequency. Transfer-defective mutations occur on the CAM plasmid, affecting both CAM and chromosomal gene transfer.

Genetic fusion of incompatible plasmids in Pseudomonas

The genes specifying enzymes responsible for the degradation of camphor and octane occur on transmissible plasmids in Pseudomonas putida strain PpG1 and P. oleovorans. Since the presence of the plasmids is vital for the oxidative metabolism of camphor or octane (by the cells) in the absence of other carbon sources, such naturally occurring, energy-generating plasmids have been designated as degradative plasmids. The two degradative plasmids, CAM and OCT, are incompatible with each other and cannot coexist in the same cell. By the use of UV irradiation and suitable selection techniques, it has been possible to fuse these two plasmids so they become part of the same replicon and coexist. Such a technique might be useful in introducing several degradative pathways in the same cell.

Microbial flora of Pacific oysters (Crassostrea gigas) subjected to ultraviolet-irradiated seawater

The ability of oysters to purge themselves of microbial contaminants was investigated by identifying the microorganisms retained by oysters after they have been subjected to ultraviolet (UV) light-treated seawater. A UV intensity of 960 muw per min per cm(2) reduced the microbial count of seawater from 263 to 13 per ml. The coliform multitube test (MPN) was reduced from a high of 17 to <0.18 per 100 ml. Over 75% of the microorganisms found in treated seawater were Acinetobacter/Moraxella, Vibrio/Pseudomonas type II, and Flavobacterium/Cytophaga. With the exception of coliforms, the microbial composition of oysters subjected to UV-treated seawater remained at levels comparable to the control oysters held in untreated seawater. Total counts ranged between 10(3) and 10(5)/g. The microorganism most frequently encountered were Flavobacterium/Cytophaga, Vibrio/Pseudomonas type II, Pseudomonas type III or IV, Acinetobacter/Moraxella, gram-positive cocci and Bacillus. Together they comprised over 90% of the flora. Coagulase-positive, deoxyribonuclease-positive, and beta-hemolytic cocci were found in some samples, as were V. parahaemolyticus, V. aliginolyticus, and Aeromonas species.

Influence of Cosmos 368 space flight conditions on radiation effects in yeasts, hydrogen bacteria and seeds of lettuce and pea

Radiobiological studies have been carried out on board the Cosmos 368 satellite, launched on 8 October 1970 and returning to earth on 14 October 1970. Yeast diploid cells Saccharomyces ellipsoides, Megri strain 139-B, haploid cells Zygosaccharomyces Baili, hydrogen bacteria Hydrogenomonas eutropha, strain Z-1, Berlin variety lettuce seeds and Capital variety pea seeds were used in these experiments. The biological specimens were irradiated with gamma-rays at dose rates of 71.8 and 6.7 rad d-1 suring the packaging of containers and after returning the samples to the laboratory. It was found that both on pre-radiation and post-radiation exposure space flight factors did not greatly influence radiobiological effects.

Repair of ultraviolet light damage by a facultative autotroph. Hydrogenomonas facilis

Hydrogenomonas facilis ATCC 15376 was shown to possess a photoreactivation system which was able to repair ultraviolet radiation damage under both heterotrophic and autotrophic conditions. Acriflavine enhanced the lethal effect of ultraviolet radiation on H. facilis.Five strains of ultraviolet-irradiated bacteriophage specific for H. facilis were photoreactivated in infected bacteria. One strain, SH6, was markedly more resistant to ultraviolet inactivation.Visible light inhibited the synthesis of bacteriophage by H. facilis except for strain SH6. Incubation of SH6-infected bacteria in the light increased the titer more than 10-fold.

Effect of Ultraviolet Light on Pectolytic Enzyme Production and Pathogenicity of Pseudomonas

Ultraviolet radiation-induced mutants of the soft rot bacterium Pseudomonas marginalis were selected for loss of pathogenicity for lettuce and witloof chicory. The avirulent mutants differed from the parent pathogen in their inability to synthesize pectolytic enzymes in culture or to ferment sodium pectate or sodium polygalacturonate as the sole carbon source in media.