Building plumbing; Hygiene; Drinking water; Bacteria; Water quality; Growth; Pipe material; Microbiomes
Neu Lisa, Proctor Caitlin R., Walser Jean-Claude, Hammes Frederik (2019), Small-Scale Heterogeneity in Drinking Water Biofilms, in Frontiers in Microbiology
, 10, 2446.
Neu Lisa, Bänziger Carola, Proctor Caitlin R., Zhang Ya, Liu Wen-Tso, Hammes Frederik (2018), Ugly ducklings—the dark side of plastic materials in contact with potable water, in npj Biofilms and Microbiomes
, 4(1), 7-7.
Proctor Caitlin R., Reimann Mauro, Vriens Bas, Hammes Frederik (2018), Biofilms in shower hoses, in Water Research
, 131, 274-286.
Ugly ducklings - The dark side of plastic materials in contact with potable water
Bath toys pose an interesting link between flexible plastic materials, potable water, external microbial and nutrient contamination, and potentially vulnerable end-users. Here, we characterized biofilm communities inside 19 bath toys used under real conditions. In addition, some determinants for biofilm formation were assessed, using six identical bath toys under controlled conditions with either clean water prior to bathing or dirty water after bathing. All examined bath toys revealed notable biofilms on their inner surface, with average total bacterial numbers of 5.5 x 106 cells/cm2 (clean water controls), 9.5 x 106 cells/cm2 (real bath toys), and 7.3 x 107 cells/cm2 (dirty water controls). Bacterial community compositions were diverse, showing many rare taxa in real bath toys and rather distinct communities in control bath toys, with a noticeable difference between clean and dirty water control biofilms. Fungi were identified in 58 % of all real bath toys and in all dirty water control toys. Based on the comparison of clean water and dirty water control bath toys, we argue that bath toy biofilms are influenced by (1) the organic carbon leaching from the flexible plastic material, (2) the chemical and biological tap water quality, (3) additional nutrients by care products and human body fluids in the bath water, as well as, (4) additional bacteria from dirt and/or the end-users’ microbiome. The present study gives a detailed characterization of bath toy biofilms and a better understanding of determinants for biofilm formation and development in systems comprising plastic materials in contact with potable water.
Small scale heterogeneity in biofilms
Three sobering facts about bacteria in our drinking water are that (1) building plumbing microbiology is not routinely monitored and (2) is essentially not covered by legislation, while (3) it is by far the most microbiologically volatile section of the entire drinking water distribution network. For example, the microbiome of stable non-chlorinated drinking water changes as much as 400% in numbers/composition at the customer’s tap due to overnight stagnation and regrowth in premise plumbing. Building plumbing microbiology is defined by (1) complex autochthonous communities, growing in (2) both biofilm and planktonic phases, (3) utilizing complex substrates under (4) dynamic oligotrophic conditions, where (5) carbonaceous nutrients migrate from the pipe surface (bottom-up supply), (6) intermittent loading of inorganic nutrients through stagnation-flushing (top-down supply) occurs, and (7) fluctuating temperatures and hydraulic conditions prevail. There exist a considerable knowledge gap in the most basic understanding of bacterial growth under the conditions described above. As a result, building plumbing microbiology is poorly understood, poorly managed, and ultimately the most critical point in the system - the point of consumption - is left extremely vulnerable. The overall goals of this project are:(1)To investigate the causes of premise plumbing microbial growth; (2)To assess the consequences that microbial growth holds for the system and for the consumers; (3)To assess potential innovative microbial management strategies for the future. This project proposes three complimentary work areas (WA) to deal with these different aspects. WA 1 (causes) will focus on the basics of bacterial growth under conditions unique to building plumbing systems. This will include a systematic investigation of planktonic and biofilm batch growth under mixed substrate and mixed community conditions, followed by modeling microbial community growth, and culminating in growth assessment in a realistic in pilot scale system. In WA 2 (consequences) we will demonstrate how selective growth on synthetic pipe materials influences community composition (richness/evenness) and subsequently the vulnerability of the microbial communities towards invasion from unwanted microbes. Moreover, we will investigate the impact of selective death (e.g., from copper pipes) on community composition and the critical question of whether this results in unwanted selection of multi-resistant bacteria. WA 3 (management) will investigate the exciting and provocative microbial management concept that a drinking water system can be purposefully pre-colonized with benign microbial communities as a so-called “probiotics”. The aim is to select and cultivate competitive “probiotic” organisms/communities, assess their ability to pre-colonize diverse plastic materials, and subsequently assess the long term stability of such bacteria during realistic operational conditions with exposure to autochthonous drinking water bacteria and invading organisms. The proposed work will have a clear academic and applied impact. A detailed understanding of autochthonous microbial community growth under low nutrient conditions with bottom-up nutrient supply does not exist and will have a broad benefit in both this specific field and related fields, leading to a new definitions and models of biofilm formation and development. The work on selection will reveal the importance of informed decision-making in the use of pipe materials for building plumbing systems. Although the “probiotics” section will not have immediate practical application - consumer acceptance may be a hindrance - it will demonstrate the extent to which communities can be managed and controlled to the benefit of the consumer, with multiple potential applications in the future.