Table 4.

The influence of zinc and copper on conjugation frequency [log₁₀(CF¹)] of an E. coli donor and a Salmonella Typhimurium recipient, calculated per donor, recipient, and total bacterial count corrected for the stress impact factor.

Minerals2 (µM)	CF(D)	CF(R)	CF(T)	CF(D) (SIF)	CF(R) (SIF)	CF(T) (SIF)
Zinc
0	−5.3 ± 0.5	−4.2 ± 0.5 a	−5.4 ± 0.5	−5.3 ± 0.5 a	−4.2 ± 0.5 a	−5.4 ± 0.5 a
153	−5.2 ± 0.3	−4.5 ± 0.2 ab	−5.3 ± 0.3	−5.7 ± 0.3 ab	−4.5 ± 0.2 ab	−5.7 ± 0.3 ab
321	−5.7 ± 0.7	−5.0 ± 0.5 bc	−5.8 ± 0.6	−6.1 ± 0.7 bc	−5.0 ± 0.5 bc	−6.1 ± 0.6 bcd
642	−5.6 ± 0.4	−4.9 ± 0.5 bc	−5.7 ± 0.4	−6.1 ± 0.4 bc	−4.9 ± 0.5 bc	−6.2 ± 0.4 c
1285	−5.4 ± 0.4	−4.4 ± 0.1 ab	−5.5 ± 0.3	−5.7 ± 0.3 abc	−4.4 ± 0.1 ab	−5.6 ± 0.3 abd
2554	−5.5 ± 0.2	−4.4 ± 0.3 ab	−5.6 ± 0.2	−5.5 ± 0.2 ab	−4.4 ± 0.3 ab	−5.6 ± 0.2 ab
p-value	0.281	−0.015	−0.192	0.006	0.015	0.002
Copper
0	−5.3 ± 0.5 a	−4.2 ± 0.5 a	−5.4 ± 0.5 a	−5.3 ± 0.5 a	−4.2 ± 0.5 a	−5.4 ± 0.5 a
173	−5.0 ± 0.2 a	−4.2 ± 0.2 a	−5.0 ± 0.2 a	−5.5 ± 0.2 ab	−4.2 ± 0.2 a	−5.5 ± 0.2 ab
346	−4.9 ± 0.6 a	−4.5 ± 0.8 a	−5.0 ± 0.6 a	−5.7 ± 0.6 ab	−4.5 ± 0.8 a	−5.7 ± 0.6 ab
677	−5.2 ± 0.4 a	−5.1 ± 0.8 a	−5.6 ± 0.5 a	−6.3 ± 0.4 bc	−5.1 ± 0.8 a	−6.4 ± 0.5 bc
1369	−6.4 ± 0.9 b	−6.9 ± 1.0 b	−7.2 ± 0.8 b	−8.0 ± 1.1 cd	−6.9 ± 1.0 b	−8.0 ± 1.0 cd
2722	−6.5 ± 0.7 b	−7.4 ± 0.9 b	−7.7 ± 0.7 b	−8.4 ± 0.9 d	−7.4 ± 0.9 b	−8.6 ± 0.9 d
p-value	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001

¹ Conjugation frequency (CF) calculated as CF/D = transconjugants/donor, CF/R = transconjugants/recipients or CF/T = transconjugants/total bacterial count; SIF = stress impact factor, ² concentrations are referring to elemental zinc and copper; p-values were calculated comparing CF of different levels of exposure to the stressor using the nonparametric Kruskal–Wallis test and Mann–Whitney test. Significant differences (p ≤ 0.05) between values are indicated by different superscript letters. Raw data are provided in supplementary data, Table S1.