Table 1

Amplification primer sequence"

Fig. 1

Construction diagram of Brucella abortus mgtC deletion strains and their recuperated strains A. PCR verification of pUCML-mgtC strain (M. DL5000 DNA marker; 1. pUCML-mgtC (PCR product is 2 000 bp); 2. Negative control); B. Brucella abortus S2308ΔmgtC deletion strain PCR verification (M. DL5000 DNA marker; 1. Brucella abortus S2308 parent strain (PCR product is 2 717 bp); 2. S2308ΔmgtC (PCR product is 2 000 bp); 3. Negative Control); C. PCR verification of pBBR1MCS-mgtC strain (M. DL5000 DNA marker; 1. pBBR1MCS-mgtC (PCR product is 917 bp); 2. Negative control); D. PCR verification of complementary strains of Brucella abortus S2308ΔmgtC(pBBR1MCS-mgtC) (M. DL5000 DNA marker; 1. S2308ΔmgtC(pBBR1MCS-mgtC) (PCR product is 917 bp); 2. Negative control); E. Brucella abortus S2308ΔmgtC strain and S2308ΔmgtC(pBBR1MCS-mgtC) gene expression were verified by qPCR"

Fig. 2

The mgtC is also a key gene in response to low Mg2+ stress in Brucella abortus A.Determination of the growth curve of Brucella abortus S2308 in high/low Mg2+ medium; B. Determination of CFU content of Brucella abortus S2308 at 4, 12 and 24 h induction in low Mg2+ environment; C. Relative expression of mgtC gene in Brucella abortus S2308 induced at 4, 12 and 24 h in low Mg2+ environment; D. Determination of growth curves of Brucella abortus S2308, S2308ΔmgtC, S2308ΔmgtC (pBBR1MCS-mgtC) in high Mg2+ environment; E. Determination of growth curves of Brucella abortus S2308, S2308ΔmgtC, S2308ΔmgtC (pBBR1MCS-mgtC) in low Mg2+ environment. *. P < 0.05; **. P < 0.01; ***. P < 0.001;ns.P>0.05"

Fig. 3

Transcriptomic analysis of Brucella abortus parent strains and MgtC deletion strains under low Mg2+ conditions A. Volcano map of mgtC gene deletion between Brucella abortus and parental strains under low Mg2+ conditions; B. Differential gene heat maps of mgtC gene deletion strains and parental strains of Brucella abortus under low Mg2+ conditions, in Fig. B, S2308 induced by low Mg2+ is labeled as S_U_1/2/3, and S2308ΔmgtC induced by low Mg2+ is labeled as C_U_1/2/3; C. GO function analysis of mgtC gene deletion between Brucella abortus and parental strains under low Mg2+ conditions, S2308 induced in low Mg2+ environment is labeled as S2308_LOW_MG, and S2308 induced in low Mg2+ environment is labeled as D_C_LOW_MG; D. Intracellular ATP content of S2308、S2308ΔmgtC, S2308ΔmgtC (pBBR1MCS-mgtC) in 107 bacteria under high/low Mg2+ environment. ns. P > 0.05;*. P < 0.05; **. P < 0.01; ***. P < 0.001"

Fig. 4

Functional analysis of MgtC in Brucella abortus resistance to environmental stress A. The survival rate of S2308, S2308ΔmgtC, S2308ΔmgtC(pBBR1MCS-mgtC) in TSB with the final concentration of hydrogen peroxide of 5.0 and 2.5 mmol ·L-1; B. The survival rate of S2308(A), S2308ΔmgtC(B), S2308ΔmgtC(pBBR1MCS-mgtC)(C) with the same amount of bacteria in acidic environment with final concentration of pH=5.5 or 4.5; C. Survival of S2308, S2308ΔmgtC, S2308ΔmgtC(pBBR1MCS-mgtC) at 25, 42 ℃, 0.4 mmol ·L-1 2, 2-bipyridine, 0.5 mmol ·L-1 SNP on TSA plates with the same bacterial content. *. P < 0.05; **. P < 0.01; ***. P < 0.001"

Fig. 5

Functional analysis of MgtC in Brucella abortus resistance to Cationic bactericidal peptides TSB survival rate of S2308, S2308ΔmgtC, S2308ΔmgtC(pBBR1MCS-mgtC) with the same amount of bacteria at the final concentration of 1 mg ·mL-1 polymyxin B. *.P < 0.05"

Fig. 6

Functional analysis of MgtC in Brucella abortus for formation of biofilms Determination of biofilm formation capacity of S2308, S2308ΔmgtC, S2308ΔmgtC(pBBR1MCS-mgtC) at 48 and 96 h under the same bacterial content. ns.P>0.05; **. P < 0.01"

Fig. 7

MgtC did not affect the intracellular viability of Brucella abortus and its pathogenicity to mice A. At 1, 4, 24, 48, 72 h after infection, S2308, S2308ΔmgtC, S2308ΔmgtC(pBBR1MCS-mgtC) intracellular bacterial CFU were detected; B. Bacterial load in spleen of S2308, S2308ΔmgtC, S2308ΔmgtC(pBBR1MCS-mgtC) mice at 2, 4, 6, and 8 weeks after infection. *. P < 0.05; **. P < 0.01; ***. P < 0.001"