Microflora of canned vegetables when using saturated salt brine as a preservative

The number and biological diversity of microorganisms in two samples of preserved using saturated salt brine fern Pteridium aquilinum was studied by direct microscopy and cultivation method. The first sample was stored for 3 months and the second sample was stored for 15 months after salting. No filamentous fungi, yeasts and spore forming bacteria were found in both samples. Total number of aerobic and facultative anaerobic bacteria able to grow on nutrition agar (peptone - 9,0 g/L, casein hydrolysate - 8,0 g/L, yeast extract - 3,0 g/L, NaCl - 5,0 g/L, Na2HPO4 - 2,0 g/L, pH 7,2±0,2) was 4400 ± 937 CFU ml- 1 in the first sample and 4950 ± 992 CFU ml -1 in the second sample. The total number of bacterial cells counted using phase-contrast microscopy was 2,556 ± 0,385 millions and 0,878 ± 273 millions per ml, respectively. The bacterial cells are rod-shaped, motile or non-motile. Cultivation in the culture media containing high salt concentration showed that these bacteria are able to grow aerobically at 15-36 % NaCl with the optimal concentration in between 20-25 % NaCl, and with the optimal growth temperature +37 °C or higher. All these facts allow us to identify these bacteria as extremely halophilic archaea belonging to the family Halobacteriaceae (domain Archaea, kingdom Euryarchaeota, phylum Euryarchaeota, class Halobacteria, order Halobacteriales). All the halobacteria in the samples are localized in the brine, whereas tissues of fern remain sterile.