Comparison of the microbiomes of two drinking water distribution systems—with and without residual chloramine disinfection

Table 1 Summary of marker gene concentrations via qPCR

Target	Statistic	Biofilms (copies cm ⁻²)		P value ^†,‡	Drinking water (copies L ⁻¹)		P value ^†	Source
		Chloraminated ^‡	No residual		Chloraminated	No residual
Bacterial 16S rRNA genes	Median	<MQL	4.5×10⁷		7.9×10⁶	2.2×10⁷
	Min.	<6.5×10⁵	1.8×10⁵	1×10⁻⁶	<1.3×10⁶	2.8×10⁶	5×10⁻³	[16]
	Max.	5.0×10⁷	4.0×10⁸		1.0×10⁸	3.5×10⁸
N. oligotropha-like amoA genes	Median	4.7×10⁴	1.1×10³		2.6×10⁴	7.9×10²
	Min.	2.0×10³	<3.2×10²	2×10⁻⁷	2.1×10³	<2.2×10²	5×10⁻¹⁰	This study
	Max.	1.0×10⁷	2.6×10⁴		4.4×10⁶	7.4×10³
Archaeal amoA genes	Median	<MQL	2.8×10⁴		<MQL	9.2×10⁵
	Min.	<1.1×10²	<1.5×10³	4×10⁻⁶	<2.3×10²	2.5×10⁴	3×10⁻¹¹	This study
	Max.	<7.1×10²	2.6×10⁵		<5.6×10²	1.4×10⁷

<MQL, less than method quantification limit; min., minimum; max., maximum
^†Group-wise comparisons (i.e., chloraminated versus no residual) using generalized Wilcoxon tests
^‡Observations from seasonal shut-off water mains are excluded

ISSN: 2049-2618