High-throughput metal susceptibility testing of microbial biofilms

BMC Microbiology

Table 3 Susceptibility of Escherichia coli JM109 to metal cations with 2 or 24 h of exposure in minimal (MSVG) medium

Periodic group	Metal ion	Exposure time (h)	MIC (mM)	MBC (mM)	MBEC (mM)	Fold Tolerance¹
7B	Mn²⁺	2	33 ± 9	> 149	> 149	na
		24		93 ± 37	84 ± 47	0.90
8B	Co²⁺	2	≤ 0.27	26 ± 10	> 139	≥ 11
		24		1.0 ± 3	1.0 ± 3	1.0
	Ni²⁺	2	≤ 0.27	> 139	> 139	na
		24		0.48 ± 0.13	0.54 ± 0.39	1.1
1B	Cu²⁺	2	≤ 0.25	≤ 0.25	≤ 0.25	na
		24		≤ 0.25	≤ 0.25	na
	Ag⁺	2	≤ 0.04	≤ 0.04	0.59 ± 0	≥ 15
		24		≤ 0.04	≤ 0.04	1.0
2B	Zn²⁺	2	≤ 0.25	11 ± 6	> 125	≥ 23
		24		0.55 ± 0.31	0.49 ± 0.35	0.89
	Cd²⁺	2	≤ 0.14	5.1 ± 2.9	> 73	≥ 29
		24		0.49 ± 0.14	1.4 ± 1.1	2.9
	Hg²⁺	2	≤ 0.02	≤ 0.02	0.05 ± 0.02	≥ 2.5
		24		≤ 0.02	≤ 0.02	1.0
3A	Al³⁺	2	nd	42 ± 40	> 304	≥ 14
		24		1.5 ± 0.6	4.0 ± 1.4	2.7
4A	Sn²⁺	2	2.2 ± 0	8.6 ± 0	8.6 ± 0	1.0
		24		4.3 ± 0	7.5 ± 2.2	1.7
	Pb²⁺	2	nd	20 ± 0	40 ± 0	2.0
		24		4.9 ± 0	1.2 ± 0	0.25

na indicates a measurement that is not applicable
bold indicates the fold tolerance at 24 h of exposure
¹the fold tolerance, given the sensitivity of the assay on a log₂ scale, is equal to the ratio of the means of MBEC:MBC₁₀₀

ISSN: 1471-2180