TABLE 2.

Expression of hydrogenase-encoding, methanogenesis-associated, and acetate assimilation-associated genes in M. conradii monoculture and syntrophic cocultures and fold change of expression levels in cocultures relative to monoculture^a

Locus tag and category	Gene name	Expression levelb (×10−3; means ±SD)					Fold changec
		M	MB1	MB2	MP1	MP2	MB1	MB2	MP1	MP2
Hydrogenases
Mtc_0802	echE	0.17 ± 0.01 B	0.54 ± 0.11 A	0.52 ± 0.17 A	0.55 ± 0.14 A	0.38 ± 0.04 AB	3.10*	2.98*	3.16*	2.17
Mtc_0470	vhtG	0.80 ± 0.06 B	0.63 ± 0.11 B	0.59 ± 0.32 B	1.56 ± 0.19 A	0.76 ± 0.38 B	0.79	0.74	1.95*	0.95
Mtc_1001	frhA1	0.05 ± 0.01	0.032 ± 0.004	0.049 ± 0.018	0.056 ± 0.023	0.046 ± 0.032	0.59	0.91	1.04	0.85
Mtc_2127	frhA2	1.55 ± 0.31 B	2.50 ± 0.29 A	2.90 ± 0.59 A	2.50 ± 0.52 A	3.05 ± 0.63 A	1.61*	1.87*	1.61*	1.96*
Mtc_2479	mvhA1	0.045 ± 0.013 B	0.061 ± 0.009 B	0.082 ± 0.028 B	0.13 ± 0.03 A	0.077 ± 0.004 B	1.36	1.83	2.97*	1.72
Mtc_0470	mvhA2	1.51 ± 0.30 C	1.77 ± 0.17 BC	2.96 ± 0.85 A	2.77 ± 0.46 A	2.59 ± 0.33 AB	1.17	1.96*	1.83*	1.72*
Methanogenesis pathway proteins
Mtc_0163	fmdB	0.0007 ± 0.0003	0.0011 ± 0.0003	0.0010 ± 0.0002	0.0011 ± 0.0004	0.0009 ± 0.0002	1.70	1.49	1.66	1.28
Mtc_2470	fwdB	1.74 ± 0.33 B	5.99 ± 1.62 A	6.75 ± 1.07 A	8.08 ± 0.79 A	7.26 ± 0.57 A	3.44*	3.88*	4.64*	4.17*
Mtc_1592	mtd	1.72 ± 0.16 B	1.87 ± 0.13 AB	2.82 ± 0.92 AB	3.16 ± 0.46 A	3.11 ± 1.38 AB	1.09	1.64	1.84*	1.81
Mtc_0135	mer	2.71 ± 0.78 B	4.99 ± 0.56 A	5.87 ± 1.21 A	5.47 ± 0.91 A	5.01 ± 1.54 A	1.84*	2.17*	2.02*	1.85*
Mtc_0943	mtrH	1.25 ± 0.06 B	2.04 ± 0.11 A	2.50 ± 0.11 A	2.36 ± 0.52 A	2.57 ± 0.61 A	1.63*	2.00*	1.88*	2.05*
Mtc_0908	mcrA	11.07 ± 0.45 C	19.37 ± 2.43 B C	30.24 ± 6.47 A	25.97 ± 4.77 AB	25.98 ± 7.43 AB	1.75	2.73*	2.35*	2.35*
Mtc_1470	hdrB1	0.0015 ± 0.0004 B	0.0042 ± 0.0019 AB	0.0040 ± 0.0023 AB	0.0055 ± 0.0015 A	0.0056 ± 0.0011 A	2.85	2.75	3.78*	3.81*
Mtc_2474	hdrB2	0.64 ± 0.18 C	2.36 ± 0.66 A	2.33 ± 0.30 A	2.30 ± 0.11 A	1.55 ± 0.18 B	3.69*	3.64*	3.60*	2.42*
Mtc_0481	hdrB3	0.095 ± 0.029 B	0.28 ± 0.11 B	0.30 ± 0.13 B	0.59 ± 0.15 A	0.61 ± 0.20 A	2.96	3.19	6.18*	6.36*
Mtc_2125	fdhA	0.44 ± 0.07 B	1.35 ± 0.14 A	2.18 ± 0.80 A	2.26 ± 0.44 A	2.28 ± 1.34 A	3.10*	4.99*	5.18*	5.22*
Acetate assimilation related proteins
Mtc_1904	acs1	0.020 ± 0.005 A	0.018 ± 0.003 A	0.013 ± 0.001 AB	0.015 ± 0.003 AB	0.009 ± 0.003 B	0.93	0.66	0.78	0.48*
Mtc_2228	acs2	0.016 ± 0.010 A	0.0021 ± 0.0002 B	0.002 ± 0.001 B	0.0015 ± 0.0004 B	0.0016 ± 0.0002 B	0.13*	0.13*	0.09*	0.10*
Mtc_1504	ppa	0.12 ± 0.03 AB	0.18 ± 0.01 A	0.17 ± 0.06 A	0.085 ± 0.042 B	0.1201 ± 0.0003 AB	1.55	1.43	0.72	1.02
Mtc_0842	porA-1	0.045 ± 0.013 B	0.12 ± 0.03 A	0.12 ± 0.04 A	0.029 ± 0.01 B	0.040 ± 0.003 B	2.58*	2.56*	0.64	0.89
Mtc_1765	porA-2	0.043 ± 0.010	0.065 ± 0.006	0.065 ± 0.024	0.038 ± 0.011	0.052 ± 0.005	1.51	1.50	0.89	1.21

^aResults shown are expression levels (normalized as ratios of mRNA transcripts to 16S rRNA) of hydrogenase-encoding genes, methanogenesis-associated genes, and acetate assimilation-associated genes in M. conradii monoculture and syntrophic cocultures with P. thermopropionicum or S. lipocalidus, as well as fold changes of expression levels in M. conradii cocultures relative to monoculture. The gene names, locus tags, and primers for PCR amplification are given in Tables S1 and S2 in the supplemental material. M, monoculture; MB and MP, syntrophic butyrate and propionate cocultures, respectively. The numbers 1 and 2 indicate the early- and mid-exponential-growth phases.

^bValues are means from three biological replicates (two for MP2) and three technical replicates for each sample; means ± SD are given. Different letters indicate significant differences (P < 0.05).

^cFor the fold change, values are the ratios of relative transcript abundance of target genes in cocultures compared to that in monoculture. An asterisk means significant difference (P < 0.05) between monoculture and cocultures.