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Mechanisms of Particle Removal from Liquid
Published in Maik W. Jornitz, Theodore H. Meltzer, Sterile Filtration, 2020
Maik W. Jornitz, Theodore H. Meltzer
As Colwell (1994) sets forth, Viable but non-culturable bacteria have been found to occur in a variety of Gram-negative bacteria, e.g. Vibrio cholerae 01 and 0139, Salmonella spp., Shigella spp., Legionellae, and Campylobacter. Because bacteria in the viable but non-culturable state are reduced in size and frequently in coccoid form, they will pass through 0.45-micron filters and in some cases, 0.2-μm filters. Furthermore, under very low nutrient conditions, the viable but nonculturable state may be predominant. Preparation of water for pharmaceutical and biotechnology applications requires consideration of the presence of bacteria in a nonculturable, dormant stage, especially for the preparation of solutions of injectables or topical reagents for use in the eye or medical therapeutics for burn victims. Water purification systems cannot rely on culturable plate counts for monitoring safety and quality. They must consider the direct count and molecular genetic assay for water safety quality.
Nanobiotechnology: An Ocean of Opportunities
Published in Rajesh Singh Tomar, Anurag Jyoti, Shuchi Kaushik, Nanobiotechnology, 2020
Mala Trivedi, Rachana Singh, Parul Johri, Rajesh K. Tiwari
There are many outbreaks of food disease reported which clearly demand to monitor food-borne pathogens throughout. The food pathogens may be present in low numbers in a sample for analysis, which makes the detection difficult. Traditional detection methods for pathogen determination like colony count estimation are laborious and time-consuming with completion ranging from 24 h for E. coli to 7 days for Listeria monocytogenes, and these pose significant difficulties for quality control of semi-perishable foods. Pathogen numbers can also be underestimated using these methods due to microorganisms entering viable but nonculturable states due to environmental stress [49]. Upon restoration from this state by, for example, an increase in temperature of the cells, microorganisms can regain the ability to cause infection, thus posing a health risk. Advances in the manipulation of these nanomaterials permit binding of different biomolecules such as bacteria, toxins, proteins, and nucleic acids [34]. One of the major advantages of using nanomaterials for biosensing is that because of their large surface area, a greater number of biomolecules are allowed to be immobilized, and this consequently increases the number of reaction sites available for interaction with a target species. This property, coupled with excellent electronic and optical properties, facilitates the use of nanomaterials in label-free detection and in the development of biosensors with enhanced sensitivities and improved response times [25].
Role of Microbes in Environmental Sustainability and Food Preservation
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Huang En, Ravi Kr. Gupta, Fangfei Lou, Sun Hee Moon
Natural antimicrobial agents, originating from animals, plants, and microorganisms, include promising alternatives to chemical food preservatives. Examples of these include ovotransferrin from egg-white, chitosan from crustaceans and arthropods, essential oils of spices and herbs, pediocin-like bacteriocin, and microbial fermentates of some starter cultures (Juneja, Dwivedi, & Yan, 2012). Table 19.2 lists some of the FDA-approved natural antimicrobial agents. Bacteria are the most productive sources for antimicrobials. Additionally, most bacteria (>99%) are not readily cultured in laboratory media (Daniel, 2005); bacteria can enter the viable-but-nonculturable (VBNC) state under adverse conditions, such as low temperature, limited nutrient, and other stresses during food processing and storage (Giraffa & Neviani, 2001). The VBNC populations are mostly an untapped resource that may present great opportunities for researchers seeking novel antimicrobial agents. Bacteriocins of lactic acid bacteria, particularly, have been investigated extensively as potential alternatives to chemical preservatives.
Emerging contaminants antibiotic resistance genes and microplastics in the environment: Introduction to 21 review articles published in CREST during 2018–2022
Published in Critical Reviews in Environmental Science and Technology, 2022
Lili Niu, Weiping Liu, Albert Juhasz, Jun Chen, Lena Ma
Recently, VBNC (viable but nonculturable) bacteria have attracted attention due to their resistance to traditional disinfection techniques, including chlorine, ultraviolet, and ozone. The horizontal transfer of ARGs can be promoted when VBNC bacteria are resuscitated under favorable external conditions, resulting in potential transfer risk. To provide a general perception of VBNC bacteria and the potential transfer of ARGs, Cai et al. (2022) reviewed the changes, health risks and environmental application of bacteria in VBNC state. They concluded that morphological changes occur in cell wall, cell membrane and cytoplasm after bacteria enter the VBNC state. However, the formation of VBNC bacteria by light-based wastewater disinfection technologies and the horizontal transfer of ARGs by VBNC bacteria require more studies.
Biomass Recovery Method for Adenosine Triphosphate (ATP) Quantification Following UV Disinfection
Published in Ozone: Science & Engineering, 2019
Kyle D. Rauch, Allison L. Mackie, Brian Middleton, Xuesong Xie, Graham A. Gagnon
Ultraviolet (UV) irradiation is often used as a final disinfection step in municipal wastewater treatment facilities (WWTFs) due to its lack of harmful effects on receiving water bodies compared to chlorination, the most widely used water disinfection method. Typical tests to determine efficacy of UV disinfection on Escherichia coli and other fecal coliforms rely on 24-h to 7-day culturability studies (APHA (American Public Health Association), AWWA (American Water Works Association, Water Pollution Control Federation), and WEF (Water Environment Federation) 2012; Chang et al. 1985; Lazarova et al. 1998). UV irradiation alters microbial DNA in such a way that they can no longer replicate or produce toxins, termed inactivation. However, organisms continue to be present in the water that has been treated and will continue to carry out their metabolic activities until their lifecycle is complete (Baron and Bourbigot 1996; Said, Masahiro, and Hassen 2010; Zhang et al. 2015). This state is referred to as viable but nonculturable (VBNC), meaning microbes are still alive and consuming energy, but would not show growth in typical tests of culturability. This is significant for WWTFs in that if a rapid test were to be carried out for quantifying microbiological contamination (or disinfection performance) the results may falsely indicate poor disinfection performance since the organisms that have been inactivated are VBNC.
Formation mechanisms of viable but nonculturable bacteria through induction by light-based disinfection and their antibiotic resistance gene transfer risk: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Yiwei Cai, Jianying Liu, Guiying Li, Po Keung Wong, Taicheng An
Light-based disinfection is a widely used disinfection technology, including for wastewater treatment, food sterilization, item disinfection, and medical equipment sterilization (Jiang et al., 2017; Sun et al., 2016). Despite its wide range of uses, it cannot completely kill bacteria under some environmental conditions, leading to the emergence of dormant bacteria (Alvear-Daza et al., 2021; Guo et al., 2019). In recent years, an increasing number of studies have reported that bacterial dormancy is an important way for bacteria to obtain antibiotic resistance (Reineke & Mathys, 2020; Wormer et al., 2019), among which viable but nonculturable (VBNC) cells are a typical dormant subpopulation. The VBNC state is considered an important strategy for bacteria to respond to environmental stimuli. In this state, bacteria cannot grow on conventional culture media, but they still survive and can be restored to a cultivable wild-type state under favorable conditions (Bodor et al., 2020; Dong et al., 2020). In recent years, bacterial regeneration after disinfection, that is, VBNC cells induced by disinfection, has attracted increasing attention (Wang, Ateia, et al., 2021). Concern is growing as to whether conventional and emerging disinfection technologies can completely eliminate pathogens. Due to their characteristically strong tolerance, VBNC bacteria cannot be completely eliminated by traditional disinfection techniques, resulting in a potential risk of ARG transfer. Once the VBNC state is induced, ARB can cause HGT after being resuscitated under certain conditions (Bodor et al., 2020; Fu et al., 2020). Therefore, while there is concern about the transfer of ARGs between conventional wild-type ARB and antibiotic-sensitive bacteria, the fact that some bacteria escape damage by disinfection technologies through dormancy and gene transfer should not be ignored.