Effect of temperature increase in bacterial and fungal communities of chlorinated drinking water distribution systems

Drinking Water Distribution Systems (DWDS) are diverse ecosystems where the majority of microorganisms live forming biofilms, which can alter the water quality if they are mobilised to the bulk water. Biofilm communities can be affected by the increase of temperature due to climate change, thus compromise the distribution of safe water. To understand the effect of temperature on biofilms in DWDS, biofilm was developed for 30 days at 16 °C and 24 °C using a full-scale experimental DWDS facility. Samples were collected at the end of the experiment from removable coupons inserted into the pipes. DNA was extracted and the 16S rRNA and ITS rRNA genes were sequenced and analysed, for the bacterial and fungal diversity respectively. Differences in bacterial and fungal diversity at both temperatures were observed at family level. At 16 °C bacterial community was dominated by Comamonadaceae (21.48 %), Pseudomonadaceae (16.41 %) and Sphingobacteriaceae (12.99 %). However, at 24 °C the most abundant family was Pseudomonadaceae (50.60 %) followed by Sphingomonadaceae (9.59 %) and Sinobacteraceae (7.82 %). Fungal diversity showed that at 16 °C the most abundant family was Nectriaceae (68.9 %), followed by Helotiales (24.5 %) and Filobasidiales (1.5 %). However, at 24 °C the community was dominated by Nectriaceae (98.15 %) and the following families showed a low relative abundance, Rhizopodaceae (0.95 %) and Cryptomycota (0.24 %). Temperature is a key factor for microbial growth in DWDS and affect the composition of the microbial communities. Temperature increase leads changes and a loss in complexity in bacterial and fungal communities of biofilms, which can affect the water quality.