THE PRESERVATION OF PSEUDOMONAS UNDER MINERAL OIL

Abstract

The use of mineral oil for the preservation of species of Pseudomonas is described. Eighty-three out of 91 (91.2%) PsewEornonas isolates remained viable for at least 66 months; 156 out of 168 (92.8%) isolates were still living after at least 46 months, and only 12 out of 170 (2.3%) isolates were non-viable after three years. An explanation is offered for variation in ability to grow and produce acid in chemically defined media containing galactose or sucrose. The ability to hydrolyze tributyrin and to reduce nitrate was stable over 66 months, regardless of whether the stock cultures were maintained under mineral oil or in yeast-extract peptone broth. However, the ability to digest milk or gelatin was frequently impaired or lost when cultures were maintained in peptone broth, although the mineral oil-preserved stock cultures remained stable in this respect. Over a nineteen month period six diagnostic biochemical characters of the oil-covered stock cultures remained stable within the limits of the experimental methods used. Data from the literature and information from other workers reveal that more complex methods of preserving pseudomonads are not particularly advantageous in regard either to viability or stability. The mechanism of the survival of bacteria under mineral oil is discussed. The taxonomic significance of the loss of proteolytic activity by the 'bench-broth' cultures of Pseudomonas spp. is illustrated by a single example. PROOM, H. & HEMMONS. L. M. (1949). The drying and preservation of bacterial cultures. J. sen. Microbiol. 3, 7. RHODES, MABEL (1950). Viability of dried bacterial cultures. J . gen. itficrobio~. 4, 450. RHODES, M. E. (1956). The classification of Pseudomom. Ph.D. thesis, University of Reading, SEER+, A. F. (1943). A method for maintaining Corynebacterium sepedonicum in culture for long May 1956. periods without transfer. Phyhpthology 33, 330.

THE RELATIONSHIP OF ORGANISMS OF THE GENUS PSEUDOMONAS TO THE SPOILAGE OF MEAT, POULTRY AND EGGS

“…MEAT OR EGQ PRODUCTS Although the pseudomonads are much more prevalent than other micro-organisms on refrigerated meat or egg products, isolates cannot be classified as to genus until a few selected biochemical reactions have been determined and the organisms have been examined microscopically to ensure that they are Gram-negative rods with polar flagella, as shown in and Rhodes (1957) have described methods whereby sharper differentiation between pseudomonads and other genera may be effected. It would be impossible to establish the validity of status for the 49 soil and fresh water pseudomonads defined in the 7th edition without thoroughly and exhaustively studying every reaction of each of these bacteria.…”

“…As has been pointed out by other workers (Seleen & Stark, 1943;Rhodes, 1959), the property of producing fluorescent pigment and of musty and/or aromatic odours is unstable and depends upon the substrate. Earlier, Rhodes (1957) pointed out that the ability of cultures to digest milk or gelatin was impaired or lost when cultures were maintained in peptone broth and put forward the hypothesis that such loss of proteolytic ability is explicable on the basis of adaptation to environment. One such factor deserving of consideration is the effect of temperature.…”

The Cytology of Pseudomonas spp. as Revealed by a Silver-Plating Staining Method

“…objective) a few threads of cotton wool held in front of the microscope lamp was a simple method for obtaining the necessary optical efficiency. Each of the Pseudornonas isolates collected was examined a t least three times by this flagella-staining technique, after various periods of maintenance (up to 59 yr.) as laboratory stock cultures preserved on yeast-extract agar slopes covered with mineral oil (Rhodes, 1957).…”