Relationship between physiochemical properties, aggregation and u.v. inactivation of isolated indigenous spores in water

Abstract

Aims: The objective of the study was to compare ultraviolet (u.v.) inactivation kinetics of indigenous aerobic spores in surface water with their laboratory-cultured spore isolates and to investigate the relationship between physicochemical characteristics and u.v. inactivation kinetics of spore isolates. Methods and Results: Lake water samples were analysed for the presence of indigenous aerobic spores. Different bacterial isolates from the heterogeneous indigenous population were genetically characterized, resporulated and examined for hydrophobicity, surface charge, particle size distribution and survival at different u.v. 254 nm fluence levels. Cultured isolated spores exhibited a three-stage inactivation curve consisting of shoulder, first order and tailing regions whereas indigenous spores exhibited only one stage of linear kinetics. Hydrophobicity of the Bacillus spore isolates was inversely related to the extent of u.v. inactivation before tailing occurred. Conclusions: Tailing in the u.v. inactivation curves results from aggregation of a portion of the spore population because of hydrophobic interactions, supporting the link between aggregation of spores, hydrophobicity and u.v. inactivation. Significance and Impact of the Study: Evidence of the link between spore physicochemical parameters and u.v. disinfection performance furthers the understanding of factors that affect inactivation of microbes in natural waters supplied to drinking water treatment plants.

UV Light Inactivation of Bacterial Biothreat Agents

“…The SSM-produced spores were less hydrophobic (P ϭ 0.25) at 64.1% (standard deviation [SD], 5.6%) than the SEA-produced spores at 76.2% (SD, 2.8%), whereas the SEA-produced Ames spores were closer (P ϭ 0.03) in hydrophobicity to the SEA-produced Sterne spores at 79.6% (SD, 3.4%). These observations agree with the previous publication (7) in that the more hydrophobic spores tend to aggregate together to a greater extent, shielding a greater number of spores from exposure to UV radiation, thereby creating a more pronounced tailing off of the inactivation curve.…”

UV-induced self-aggregation of E . coli after low and medium pressure ultraviolet irradiation

“…One of the possible explanations for the tailing phenomenon is the presence of aggregates. Aggregation of cells with other cells may be induced by the UV treatment [4,1,16] or microbes may be associated with particulate matter [19,9,[12][13][14]6,7,11,15,18].…”

“…However, in water and wastewater disinfection, often a survival curve characterized by the shoulder effect at low UV doses and tailing at high UV doses is encountered [23,20,16]. Tailing refers to the presence of a residual surviving population of microorganisms even at very high UV doses, and is therefore a public health concern.…”

Array lead zirconate titanate/glass piezoelectric microcantilevers for real-time detection of Bacillus anthracis with 10 spores/ml sensitivity and 1/1000 selectivity in bacterial mixtures

“…This use of polycarbonate and silicone was designed to prevent interactions of the BA spores with surface of the flow chamber, thus enhancing the efficiency of delivery of analyte to the PEMS array biosensor surface. The surface charge of BA spores as well as that of polycarbonate and silicone rubbers is well characterized and all are negative at neutral pH, [32][33][34] such as is the case in the de-ionized ͑DI͒ water used for experimentation herein. Thus no "sticking" of the BA to the flow system walls was expected and indeed, no adverse effects from such possible sticking was observed.…”