The bacterial flora of non-carbonated, natural mineral water from the springs to reservoir and glass and plastic bottles.

Quantitative and qualitative determinations of the bacterial flora of non-carbonated natural mineral water at the most important steps during bottling at a large water source yielded the following results: (i) Colony counts (on 1:10 diluted plate count agar, incubated at 20 degrees C for 14 days) for water of the five springs and the mixed water were less than 1 to 4 cfu ml-1. The Gram-negative bacterial flora (n = 50 isolates) showed a very different but constant spring specific species distributions with predominance of either eutrophic fluorescent pseudomonads, oligotrophic non-fluorescent pseudomonads or oligotrophic yellow bacteria. (ii) In the reservoir and immediately after bottling the counts were in the range of 10 cfu ml-1. But nearly 30% of the species of the spring water were no longer detectable and there was a significant increase of Gram-positive bacteria. (iii) After 1 week of storage at 20 degrees C colony counts of more than 10(5) cfu ml-1 were found in plastic bottles, but only about 10(4) cfu ml-1 in glass bottles. Besides, a very distinct change of the composition of the microflora occurred. In glass bottles slow-growing oligotrophic non-fluorescent pseudomonads, yellow bacteria and Acinetobacter predominated. In plastic bottles fast-growing eutrophic and mesotrophic fluorescent pseudomonads, Flexibacter and Acinetobacter were dominating. In mineral water, bottled into thoroughly cleaned glass bottles, colony counts of more than 10(5) cfu ml-1 were found within 4 days. In bottles, cleaned mechanically as usual, the increase was significantly slower with a maximum of only 5 x 10(3) cfu ml-1 after 8 days. The results of inoculation experiments in sterile filtered mineral and distilled water led to the suggestion that the difference between the two types of bottles is caused firstly by an inhibition of growth due to residues of cleaning detergents in the glass bottles. Growth promotion by dissolved organic substances in the plastic bottles only played a minor role. After repairing of the pump at a depth of 300 m in a warm mineral water spring, the colony counts at 20, 37 and 42 degrees C on 1:10 diluted and normal plate count agar increased beyond the limits required by the EC directive for mineral water stored a month. Then colony counts decreased slowly and reached the initial level after 1 year, except for the colony counts 1:10 diluted agar at 20 degrees C which stabilized at a relatively high number and a significant alteration of the microflora.(ABSTRACT TRUNCATED AT 400 WORDS)

A simple nutrient-tolerance (NT) test for the characterization of the different types of oligocarbotolerant and oligocarbophile water bacteria from non-carbonated mineral water.

Comparative determination of the specific growth kinetics in mineral water and low and higher concentrated broths at 20 degrees C of 25 selected Gram-negative bacteria isolated from natural non-carbonated mineral water yielded three groups: (1) facultative oligocarbotolerants--with faster growth in normal broth (In g l-1: yeast extract 2.5; casein peptone 5.0; glucose 1.0); (2) obligate oligocarbotolerants--with equal rates of growth in normal and 1:10 diluted broth; and (3) oligocarbophiles--with faster growth in 1:10 diluted broth and in mineral water. In addition, three nutrient types, 'eu-, meso- and oligotrophic' could be distinguished on the basis of full, weak and no growth in brain-heart infusion broth. Further characterization was made between slow and very slow growth types in 1:10 diluted broth. All 25 isolates were psychrotrophic with a minimum growth temperature below 0 degree C. The optimum and maximum temperatures of growth in 1:10 diluted broth, as determined in a temperature gradient incubator were between 20 and 32, and between 29 and 34 degrees C with an average of 26 and 31 degrees C, respectively. Based on these results a very simple nutrient-tolerance test was proposed. After inoculation of the three media, 1:10 diluted broth, normal broth and brain-heart infusion, it is only necessary to check whether or when visible turbidity occurs during 2 weeks incubation at 20 degrees C. This allows additional characterization of bacteria from natural mineral water, which are often difficult to identify, on the basis of growth characteristics in various types of nutrient media.