Survival of natural sewage populations of enteric bacteria in diffusion and batch chambers in the marine environment

The survival of natural populations of Escherichia coli and enterococci in sewage was measured in large-volume diffusion chambers in an estuary and a salt marsh. The 5-liter chambers, with polycarbonate membrane sidewalls, were found to be suitable for up to week-long experiments. Decay rates, measured monthly from February to August 1978, ranged from 0.042 to 0.088 h(-1) (time for 90% of the population to die = 25 to 55 h) for E. coli and 0.019 to 0.083 h(-1) (time for 90% of the population to die = 29 to 122 h) for enterococci and were significantly correlated with temperature. In contrast to the diffusion culture experiments, the decay of E. coli in batch culture did not correlate with temperature. Enterococci survived longer than E. coli in the Narragansett Bay (estuary) experiments, but survived less well in the more eutrophic salt marsh. The effect of light on survival was examined with light/dark experiments and sampling at frequent intervals over the diel cycle. Diel changes in survival were not evident in the Narragansett Bay experiments. E. coli, however, exhibited a diel pattern of growth during the day and death at night in the salt marsh. There was no significant difference in decay rates between light and dark diffusion chambers, nor were decay rates correlated with light intensity. In concurrent batch experiments, survival was significantly greater in the dark for both organisms. These results suggest that the effect of light is complex and that conditions in batch culture may modify the survival of enteric bacteria. Observations made in diffusion chambers may more closely follow the in situ survival of enteric microorganisms.     

Survival of enteric bacteria in seawater

Enteric bacteria exposed to the marine environment simultaneously encounter a variety of abiotic and biotic challenges. Among the former, light appears to be critical in affecting seawater survival; previous growth history plays a major part in preadaptation of the cells, and stationary phase cells are generally more resistant than exponentially growing ones. Predation, mostly by protozoa, is probably the most significant biotic factor. Using Escherichia coli as a model, a surprisingly small number of genes was found that, when mutated, significantly affect seawater sensitivity of this bacterium. Most prominent among those is rpoS, which was also dominant among genes induced upon transfer to seawater.     

Photosynthetic response and recovery of Antarctic marine benthic microalgae exposed to elevated irradiances and temperatures

Exposure to high temperatures affects the photosynthetic processes in marine benthic microalgae by limiting the transport of electrons, thus reducing the ability of the cell to use light. This causes damage to the Photosystem II (PSII) and may lead to photoinhibition. However, the PSII of benthic microalgal communities from Brown Bay, eastern Antarctica, were relatively unaffected by significant changes in temperature. Benthic microalgae exposed to temperatures up to 8°C and an irradiance of 450 μmol photons m⁻² s⁻¹ did not experience any photosynthetic damage or irreversible photoinhibition. The effective quantum yield (∆F/F _m′) at 8°C (0.433 ± 0.042) was higher by comparison to cell incubated at −0.1°C (0.373 ± 0.015) with similar irradiances. Temperatures down to −5°C at a similar irradiance showed a decrease in photosynthesis with decreasing temperature, but no severe photoinhibition as the cells were able to dissipate excess energy via non-photochemical quenching and recover from damage. These responses are consistent with those recorded in past studies on Antarctic benthic microalgae and suggest that short-term temperature change (from −5 to 8°C) will not do irreversible damage to the PSII and will not affect the photosynthesis of the benthic microalgae.     

Survival and detection of bacteria in an aquatic environment.

A genetically engineered plasmid, pPSA131, was used as a DNA probe to detect homologous DNA in Escherichia coli HB101(pPSA131) after it was mixed with aquatic microorganisms from Lake Mead, Nevada, water samples. An isolate from the pLAFR1 chromosomal library of Pseudomonas syringae Cit 7 was used to detect parent P. syringae Cit 7 that had been mixed with Lake Mead water. E. coli(pPSA131) was kept in variously treated samples of lake water or buffer, and its survival was measured by viable cell counting on modified Luria-Bertani (LB) agar. Full-strength LB agar proved better than 0.1 x LB agar at recovering E. coli(pPSA131) after survival in low-nutrient environments. Survival of E. coli(pPSA131) remained high in filtered (0.22-micron pore size) lake water and salts buffer on both selective and nonselective agars but was lower in untreated lake water or lake water filtered with a 0.8-micron-pore-size membrane. Total recoverable colonies grown on LB agar were higher when lake water was filter treated (0.8-micron pore size) than when lake water was untreated. Microorganisms recovered from lake water alone grew rapidly on nonselective media, probably because of the "bottle effect." After being mixed with Lake Mead water, E. coli(pPSA131) and P. syringae were detected by colony blotting with non-radioactively labeled DNA probes. E. coli(pPSA131) were recovered at three times during 48 h from variously treated samples of lake water and from a mixture with Lake Mead water organisms. Colonies were supported on either nonselective or selective agar for comparison.(ABSTRACT TRUNCATED AT 250 WORDS)     

Survival of human enteric viruses in the environment and food

Human enteric pathogenic viruses can enter the environment through discharge of waste materials from infected persons, and be transmitted back to susceptible persons to continue the cycle of disease. Contamination of food with viruses may also promote disease outbreaks. A number of studies have investigated the survival characteristics of several enteric viruses in various environments and foodstuffs, to help explain the transmissibility of these pathogens. This review deals with published work on enteric virus survival on fomites, and in waters, soil, and foods; the results of these studies have illustrated the robust survival of viruses in these environments. Much information is lacking, however, especially for foodstuffs and soils, and no detailed information is available concerning the survival of noroviruses, the most significant foodborne type.     

The acute physiological response of polar bears to helicopter capture

Many wildlife species are live captured, sampled, and released; for polar bears (Ursus maritimus) capture often requires chemical immobilization via helicopter darting. Polar bears reduce their activity for approximately 4 days after capture, likely reflecting stress recovery. To better understand this stress, we quantified polar bear activity (via collar-mounted accelerometers) and body temperature (via loggers in the body core [T_abd] and periphery [T_per]) during 2–6 months of natural behavior, and during helicopter recapture and immobilization. Recapture induced bouts of peak activity higher than those that occurred during natural behavior for 2 of 5 bears, greater peak T_per for 3 of 6 bears, and greater peak T_abd for 1 of 6 bears. High body temperature (>39.0°C) occurred in T_per for 3 of 6 individuals during recapture and 6 of 6 individuals during natural behavior, and in T_abd for 2 of 6 individuals during recapture and 3 of 6 individuals during natural behavior. Measurements of T_abd and T_per correlated with rectal temperatures measured after immobilization, supporting the use of rectal temperatures for monitoring bear response to capture. Using a larger dataset (n = 66 captures), modeling of blood biochemistry revealed that maximum ambient temperature during recapture was associated with a stress leukogram (7–26% decline in percent lymphocytes, 12–21% increase in percent neutrophils) and maximum duration of helicopter operations had a similar but smaller effect. We conclude that polar bear activity and body temperature during helicopter capture are similar to that which occurs during the most intense events of natural behavior; high body temperature, especially in warm capture conditions, is a key concern; additional study of stress leukograms in polar bears is needed; and additional data collection regarding capture operations would be useful.     

Influence of enteric bacteria conditioned media on recovery of Escherichia coli O157:H7 exposed to starvation and sodium hypochlorite

AIMS: To examine the effect that starvation and sodium hypochlorite stress have on virulence of Escherichia coli O157:H7 and the influence of conditioned media on recovery of stressed cells. METHODS AND RESULTS: Escherichia coli O157:H7 was starved for 5 days then exposed to 1 microg ml(-1) sodium hypochlorite, suspended in defined media Dulbecco's Modified Eagle's Medium supplemented with conditioned media, sampled over a 12-h period; and assayed for growth, production of Shiga toxin (Stx), and attachment to HCT-8 cells. During recovery, stressed and control cells grown in conditioned media exhibited greater attachment efficiencies to HCT-8 cells then cells in DMEM alone. Production of Stx by treated cells mimicked Stx production by control cells suggesting that components of conditioned media assist in recovery. Results showed that levels of autoinducer-2 fluctuate during recovery and growth suggesting involvement of a quorum sensing mechanism during the recovery of stressed E. coli O157:H7. CONCLUSIONS: The recovery of stressed E. coli O157:H7 exposed to starvation conditions and HOCl is positively affected by the presence of autoinducer-2 thereby influencing virulence factor production. SIGNIFICANCE AND IMPACT OF THE STUDY: Food-borne pathogens in a stressed state prior to ingestion can rapidly recover in the presence of bacterial by-products; exhibiting virulence characteristics and presenting a microbial food safety hazard.     

Conservation of Chi cutting activity in terrestrial and marine enteric bacteria

Homologous recombination in Escherichia coli occurs at increased frequency near Chi sites, 5'G-C-T-G-G-T-G-G3'. Cutting of DNA close to the Chi sequence by the E. coli RecBC enzyme is essential to Chi's stimulation of recombination. We have detected Chi-dependent cutting activity in extracts of several genera of terrestrial enteric bacteria (family Enterobacteriaceae) and of two genera of marine enteric bacteria (family Vibrionaceae). More distantly related bacteria had no detectable Chi-dependent cutting activity. These results support the view that recognition of this specific nucleotide sequence as a signal activating recombination has been maintained during the evolution of certain groups of bacteria. We discuss the possibility that other sequences play a similar role in other groups of bacteria.     

Isolation and characterization of surfactant degrading bacteria in a marine environment

Abstract Sea water and sediment samples taken near the coasts of Hyeres bay (France) were used for anionic surfactant titrations with surface and bottom waters and the finest part of sediments. The capacity for surfactant degradation by the 'in situ' microflora was evaluated. By using a selective plating technique 26 strains able to utilize anionic surfactant were isolated from the selected bacterial communities. Their ability to degrade anionic surfactant was verified according to the biodegradation standard method. Isolated strains were characterized by morphological and physiological properties using API 20 NE micro-method. All tested strains were Gram negative, strictly aerobic, rod or helical shaped. Their weak utilization of phenolic substrates suggests that they degrade preferentially the alkyl chain of the surfactant molecule. Biodegradation was more efficient with bacterial communities rather than with any isolated strains. Such observations indicate that complete mineralization involves several other so far non-isolated strains which complete the degradation initiated by the isolated strains.     

Survival of enteric bacteria and coliphage MS2 in pure human urine

Aims:  The survival of Escherichia coli , Salmonella enterica serovar Typhimurium, Enterococcus faecalis and coliphage MS2 was studied in stored, fresh and diluted (1 : 1) human urine at 15 and 30°C.
Methods and Results:  Survival rate was studied by the plate count method. All the organisms showed rapid inactivation in stored urine, but they survived better in diluted and fresh urine. The high pH level and temperature were the major factors found to influence the survival of the micro-organisms with the survival rate being higher at 15°C than at 30°C.
Conclusions:  The destruction of all micro-organisms in stored urine required <1 week at 30°C. Thus, the storage of urine is a useful way to reduce the risk of contamination while using urine as a fertilizer.
Significance and Impact of the Study:  The urine fertilization is aimed for the developing countries and the high temperatures in these countries may hasten the destruction of micro-organisms in urine. On the contrary, a higher survival rate of these organisms in fresh and diluted urine is a public health concern because the dilution of urine with water is likely to happen during flushing.     

Survival and detection of bacteria in an aquatic environment

A genetically engineered plasmid, pPSA131, was used as a DNA probe to detect homologous DNA in Escherichia coli HB101(pPSA131) after it was mixed with aquatic microorganisms from Lake Mead, Nevada, water samples. An isolate from the pLAFR1 chromosomal library of Pseudomonas syringae Cit 7 was used to detect parent P. syringae Cit 7 that had been mixed with Lake Mead water. E. coli(pPSA131) was kept in variously treated samples of lake water or buffer, and its survival was measured by viable cell counting on modified Luria-Bertani (LB) agar. Full-strength LB agar proved better than 0.1 x LB agar at recovering E. coli(pPSA131) after survival in low-nutrient environments. Survival of E. coli(pPSA131) remained high in filtered (0.22-micron pore size) lake water and salts buffer on both selective and nonselective agars but was lower in untreated lake water or lake water filtered with a 0.8-micron-pore-size membrane. Total recoverable colonies grown on LB agar were higher when lake water was filter treated (0.8-micron pore size) than when lake water was untreated. Microorganisms recovered from lake water alone grew rapidly on nonselective media, probably because of the "bottle effect." After being mixed with Lake Mead water, E. coli(pPSA131) and P. syringae were detected by colony blotting with non-radioactively labeled DNA probes. E. coli(pPSA131) were recovered at three times during 48 h from variously treated samples of lake water and from a mixture with Lake Mead water organisms. Colonies were supported on either nonselective or selective agar for comparison.(ABSTRACT TRUNCATED AT 250 WORDS)     

Survival and efficacy of steinernema carpocapsae in an exposed environment

Factors affecting the persistence and activity of the infective juveniles (IJs) of the nematode Steinernema carpocapsae ’Mexican’ strain on the foliage of bean plants were determined at 45, 60 and 80% relative humidity (RH). The rate of nematode mortality was related to the RH. A gradual reduction in nematode survival was recorded during a 6 h exposure period at 80% and 60% RH, whereas at 45% RH high mortality was observed within 2 h. Addition of the antidesiccant ‘Folicote’ (6% w/w) to the nematode suspension was most effective in ensuring IJ survival at 60% RH, resulting in 38–60% increase in viability during 6 h of exposure. At 80% RH ‘Folicote’ treatment resulted in only 10–20% increase in IJs viability, as compared with non‐treated IJs. At 45% RH, ‘Folicote’ treatment did not significantly increase IJ survival (P>0.05). Survival of the IJs on tomato and soybean leaves was 30–35% higher than of those recovered from leaves of cotton, pepper and bean as well as from filter paper. At 60% RH, IJ movement ceased within 45–60 min of exposure and the nematode body shrank. However, nematode pathogenicity remained almost unaltered up to 4 h of exposure, resulting in 75% mortality of larvae of the Egyptian cotton worm Spodoptera littoralis. A drastic reduction in the nematodes’ efficacy was recorded when the insects were introduced 6 and 8 h after nematode application.     

Survival of the marine crab,scylla serrata exposed to thermal shock under different experimental conditions

Survival of the edible crab, Scylla serrata Subjected to endocrinological and pharmacological procedures, was examined after exposing them to 40°C for 3 hr. Only normal, intact crabs could withstand the thermal shock but not reserpinized intact, eyestalkless, sinus glandectomised (SGE), SGE and reserpinized (RSP), SGE injected with sinus gland homogenate and SGE injected with SG homogenate and reserpinized crabs. The possible involvement of endocrine centres in S. serrata in sustaining the environmental thermal shock is discussed.     

Chitin utilization by marine bacteria. A physiological function for bacterial adhesion to immobilized carbohydrates.

Chitin turnover is essential for recycling carbon and nitrogen in marine ecosystems. A key step in this process is the adhesion of marine bacteria to chitin-containing particulates. Vibrio species were therefore surveyed for their ability to bind to immobilized carbohydrates, and one, Vibrio furnissii, adhered to glycosides of three sugars, N-acetylglucosamine (the preferred ligand), D-mannose, and D-glucose. A single Ca(2+)-requiring lectin is responsible for binding to the three sugars. Cells adhering to the chitin analogue divided at the same rate as cells in liquid culture. The first progeny of adherent cells continued to bind to the beads, but the population gradually shifted to a large fraction of free swimming cells, a process that may be necessary for colonization. Metabolic energy is required for cell adhesion to the glycosides, and transient (or no) adhesion occurred in incomplete growth media. The results were explained by studying met and pro mutants. Both the initiation and maintenance of lectin-mediated adhesion requires continuous protein synthesis; expression of lectin activity is a major priority of these cells and functions under conditions adequate for minimal protein synthesis, but insufficient to support cell growth. The adhesion/deadhesion apparatus is apparently used to continuously monitor the nutrient status of the environment, i.e. as a nutrient sensorium. In incomplete medium, cells deadhere, presumably to migrate to a more favorable environment.     

Growth and physiological response of Arundo donax L. to controlled drought stress and recovery

Soil water deficit constrains crop growth more than any other abiotic stress, both per se and in combination with other factors, making drought resistance a key element for the successful exploitation of marginal areas. Arundo donax (Poaceae), is a mesophyte that can adapt to a wide variety of ecological conditions, although its growth can be retarded by a shortage of water. The objective of the present research is to draw a comprehensive picture of the integrated response mechanisms of A. donax to controlled drought conditions, and characterize its ability to recover upon rewatering in terms of photochemical efficiency. Plants were subjected to a gradually applied drought stress for a period of three weeks, after which they were returned to fully hydrated soil conditions for one week. Overall, plant dry weight and key growth parameters were not significantly affected. However, detrimental effects were visible in the form of impaired leaf gas exchange, which influences the performance of photosynthesis, and pre-dawn leaf water potential (pdΨ_W), ?92.1% of net CO₂ assimilation rate and ?0.36 MPa, respectively at the cessation of stress. Nonetheless, a rapid restoration of A. donax physiological functions was observed upon rewatering, testifying to the environmental plasticity of this species.