Fig. 3

Legionella spp. community structure and composition shows an inverse relation to sodium concentration. Next-generation sequencing (NGS) was performed using Legionella spp.-specific 16S primers. Water (n = 40) and biofilm (n = 25) samples were analyzed separately. Spring clusters: Tiberias Hot Springs (n = 20), Haon borehole (n = 4), Fuliya (n = 8), and Tabgha (n = 33). a + b Alpha diversity of Legionella spp. across a spring clusters and b collection dates. Shannon’s entropy is presented for water and biofilm samples. Faith’s PD, Pielou’s evenness, and observed ASVs are presented in Supplementary Fig. 10a and b. Kruskal–Wallis test results and post hoc via Wilcox tests are presented in Supplementary Table 13. c Venn diagram of Legionella ASVs (minimum of 20 reads) in water and biofilm samples, according to spring cluster. d Relative abundance of Legionella ASVs, according to spring cluster and collection dates. Legionella ASVs were pre-filtered to a minimum frequency of 20 (top panel) or 2000 (bottom panel) reads. Samples are ordered by date, faceted vertically by spring cluster and horizontally by water and biofilm. As numerous ASVs (1073) were included in the construction of each barplot, colors are repetitive and are not indicative of specific ASVs. The identity of the most abundant ASVs is presented in Fig. 4a,b and Supplementary Data 4. White barplots indicate Legionella ASVs were not detected. Biofilm sampling was not possible for Tiberias Pump, Haon borehole, and Barbutim stations. For Nur station, only biofilm from September 2017 was available. e + f Beta diversity of Legionella spp. microbial population across spring clusters. Jaccard (e) and Bray–Curtis (f) are presented for water and biofilm samples. Beta diversity statistical significance was tested via PERMANOVA and PERMDISP analyses (Supplementary Tables 14 and 15). THS = Tiberias Hot Springs. Significance level; * p ≤ 0.05; ** p ≤ 0.01; *** p ≤ 0.001, **** p ≤ 0.0001