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AIMS: To develop a novel, rapid and effective screening method for chitinase producing bacteria. METHODS AND RESULTS: A simple and rapid technique for screening of potential chitinolytic bacteria has been developed using the chitin binding dye calcofluor white M2R in chitin agar. Microorganisms possessing high chitinolytic potential gave a clear zone under ultraviolet light after 24-48 h of incubation. This method was successfully applied for isolating the hyperchitinase mutant of Alcaligenes xylosoxydans. The mutant Alc. xylosoxydans EMS 33 was found to produce 3.4 times more chitinase than the wild type. CONCLUSIONS: In this study, the screening method for chitinase producing bacteria has been developed and it was applied to screen chitinase-overproducing mutant of Alc. xylosoxydans. SIGNIFICANCE AND IMPACT OF THE STUDY: The novel screening method for chitinase producer is more sensitive, rapid, user-friendly and reliable, which can also be used for screening of recombinants having chitinase gene.

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We have investigated the possibility of growing mutator phages from Pseudomonas aeruginosa on various isolates of Alcaligenes eutrophus. Although none out of 10 A. eutrophus strains were susceptible to infection with any of the phages tested, phage D3112 could be readily transferred in our model strain CH34 by means of an RP4::D3112 plasmid. CH34/RP4::D3112 lysogens were stable and produced phages. However, neither mitomycin C nor UV treatment increased the phage yield.

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A 60Co source was used to determine the effects of thermoradiation on Achromobacter aquamarinus, Staphylococcus aureus, and vegetative and spore cells of Bacillus subtilis var. globigii. The rate of inactivation of these cultures, except vegetative-cell populations of B. subtilis, was exponential and in direct proportion to temperature. The D10 (dose that inactivates 90% of the microbial population) value for A. aquamarinus was 8.0 Krad at 25 degrees C and 4.9 Krad at 35 degrees C. For S. aureus, D10 was 9.8 and 5.3 Krad at 35 and 45 degrees C, respectively. Vegetative cells of B. subtilis demonstrated a rapid initial inactivation followed by a steady but decreased exponential rate. The D10 at 25 degrees C was 10.3 Krad, but at 35 and 45 degrees C this value was 6.2 and 3.8 Krad, respectively. Between 0 and 95 Krad, survival curves for B. subtilis spores at 75 degrees C showed slight inactivation, increasing in rat at and above 85 degrees C. The D10 values for spores at 85 and 90 degrees C were 129 and 92 Krad, respectively. Significant synergism between heat and irradiation was noted at 35 degrees C for A. aquamarinus and 45 degrees C for S. aureus. The presence of 0.1 mM cysteine in suspending media afforded protection to both cultures at these critical temperatures. On the other hand, cysteine sensitized B. subtilis spores at radiation doses greater than 100 Krad. The combined effect of heat and irradiation was more destructive to bacteria than either method alone.

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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.

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A highly efficient transformation system has been demonstrated in a strain of Acinetobacter calco-aceticus (Bacterium anitratrum). During mixed growth of various stable, unencapsulated, mutant strains, deoxyribonucleic acid (DNA) is liberated and fully encapuslated transformants can be isolated. Purified DNA preparations have been used to transform suitable recipient mutant strains for ability to synthesize capsules, ability to dispense with a growth factor requirement, and resistance to streptomycin. When the wild-type strain is deprived of its capsule, either by mechanical stripping or by mutation, the unencapsulated cells tend to form large clumped masses. A nonclumping mutant of an unencapsulated strain has been isolated. When ability to synthesize capsules is transformed into this nonclumping strain, the resultant cells no longer form chains, unlike the wild-type encapsulated strain. It appears likely that the occurrence of transformation during growth of mixed cultures, with glucose or gluconate as the carbon source, may be the result of osmotic rupture resulting from the inability of unencapsulated strains to oxidize triose phosphates as fast as they are formed. The finding of transformation in Acinetobacter may provide an additional useful organism for the study of this mode of genetic transfer since this strain grows well in a simple mineral medium containing a single oxidizable source of carbon. Furthermore, no special supplementary factors seem to be required for transformation to take place.

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