Influence of Environmental Stress on Enumeration of Indicator Bacteria from Natural Waters

Abstract

The problems associated with recovery of pure cultures of Escherichia coli and Streptococcus faecalis from stream environments were examined utilizing membrane filter chambers. It was observed that upon exposure to the aquatic environment a significant proportion of cells lost their ability to produce colonies on a selective medium, yet retained this capability on a nutritionally rich, nonselective medium. Discrepancies in colony-forming units between nonselective and selective media indicated that a substantial portion of bacterial cells may become physiologically injured due to the environmental stress imposed by the aquatic environment. The extent of injury was observed to vary considerably among the eight different stream environments, since the amount of injury was not uniform for all types of water environments examined. It was observed that the injury acquired by a population of E. coli, during exposure to the aquatic environment, could be rapidly repaired in a nutritionally rich, nonselective medium. As the injured population of cells was exposed to the rich, nonselective broth, increasing proportions of cells were able to repair themselves such that they became insensitive to inhibitory agents in selective media.

The effects of nutrients on the survival of Escherichia coli in lake water

“…6c and 6d). It was not possible to determine freshwater microcosms or in situ are temwhether there was an increase in survival at perature and/or nutrient availability 15°C as the experiment was terminated before (Bissonnette et al 1975;Mancini 1978; Flint any difference would have become apparent. 1987).…”

“…Flint (1987) showed that in the absence of other bacteria, i.e. in the absence of competitors, in sterile autoclaved river water E. coli could Discussion survive for up to 260 d, even at 2 5 T , without The factors which are considered most likely to any decline in numbers and without suffering affect the survival of non-indigenous bacteria in any of the apparent stress symptoms seen by others (Bissonnette et al 1975(Bissonnette et al , 1977Zaske et al 1980). As expected, the addition of a complex mixture of nutrients, in the form of synthetic sewage, to filtered-autoclaved lake water allowed the E. coli to increase in numbers in proportion to the amount of synthetic sewage added.…”

Natural inactivation of Escherichia coli in anaerobic and reduced groundwater

“…mTEC agar). Ingredients in culture media, similar to Cook and Bolster (2007) those in mTEC agar (Zimbro et al 2009), have been shown to inhibit the growth and overall recovery of indicator bacteria, including E. coli, (Bissonnette et al 1975;LeChevallier et al 1983;McFeters 1990;Lisle et al 1998;McFeters and LeChevalier 2000). To provide some insight into the extent that recovery media inhibited the growth of E. coli following exposure to groundwater from the UF and APPZ, data from mTEC agar were compared to data from the nonselective medium R2A agar.…”

The Bacterial Flora in Bottled Natural Mineral Water Sold in Italy

“…Within the aquatic systems, allochthonous pathogenic bacteria and sanitary indicator organisms may be injured by starvation or by exposure to a range of factors such as suboptimal temperature, salinity and pH (McFaters and Singh 1991). For example, E. coli cells may remain viable but lose the ability to grow on selective media; however these cells may still be culturable on nonselective nutrient medium (Bissonnette et al 1975).…”