SURVIVABILITY AND LONG-TERM PRESERVATION OF BACTERIA IN WATER AND IN PHOSPHATE BUFFERED SALINE

Authors: LIAO, CHING HSING; SHOLLENBERGER, LISA

Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2003
Publication Date: 3/14/2003
Citation: LIAO, C., SHOLLENBERGER, L.M. SURVIVABILITY AND LONG-TERM PRESERVATION OF BACTERIA IN WATER AND IN PHOSPHATE BUFFERED SALINE. LETTERS IN APPLIED MICROBIOLOGY. 2003. V. 37. P. 45-50.

Interpretive Summary: Preservation of bacterial cultures is a routine and important task for most microbiological laboratories engaged in research and/or teaching. It has been previously reported that certain strains of plant-associated bacteria can survive in water for several years. It has not been determined, however, if water may be used to store bacteria of clinical or environmental importance. In this study, over 140 strains of bacteria capable of causing disease either in plants or in humans were tested for their ability to survive in water and in a simple salt solution called PBS. Almost all of the bacteria tested were able to survive in pure water at room temperature for several months and up to 16 years. The vast majority of Gram-negative bacteria (= bacteria that react negatively to Gram staining) tested can be preserved either in water or in PBS. However, the Gram-positive bacteria should be preserved in PBS but not in water. Preservation of bacteria in water or PBS provides a simple, convenient, and economical alternative for storage of bacterial cultures. The study also demonstrates the importance of proper disinfection treatments required to eradicate harmful bacteria in water to be used for drinking or food processing.

Technical Abstract: The stationary-phase bacterial cells collected from a rich agar medium were transferred to 10 ml of sterile distilled water or phosphate buffered saline (PBS; pH 7.2) in a screw-cap tube. The tubes were then sealed with Parafilm membrane and stored in the dark and at room temperature. The viable cells in water or PBS suspension were determined after storage for different periods of time. Almost all of the bacteria tested (144 strains), including Pseudomonas fluorescens, Pseu. viridiflava, Erwinia spp., Xanthomonas campestris, Cytophaga johnsonae, Salmonella spp., Yersinia enterocolitica, Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus, were able to survive in water for months and up to 16 years. A 30-week storage study showed that while almost all of the Gram-negative bacteria appeared to survive equally well in water and in PBS, the population of a Gram-positive [G(+)] bacterium, List. monocytogenes, declined more rapidly in water than in PBS. A 5-week storage study with another G(+) bacterium (Staph. aureus) confirmed the above observation. The viability of both plant- and human-pathogenic bacteria can be maintained in sterile distilled water or PBS for several years and Gram-positive bacteria appear to survive better in PBS than in water. The preservation method described here is simple, convenient, and economical and represents a suitable alternative to conventional methods for storage of bacterial cultures.