Variations in the Expression of the L-lactate Dehydrogenase Gene during the Different Phases of Lactococcus lactis KLDS4.0325 Growth
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Abstract:
The expressions of three L-lactate dehydrogenase genes at the mRNA transcription level during the different phases of Lactococcus lactis KLDS4.0325 growth were investigated in this study. Dynamic variations in the expressions of the three L-lactate dehydrogenase genes (ldh , ldhB, and ldhX) during the different growth phases were detected by fluorescence-based quantitative real time polymerase chain reaction (PCR), using the 16s rRNA gene as the internal standard. The growth curves of the strain were observed to be ‘S’-shaped, with the strains reaching the exponential phase of growth within 2~6 h of culture; subsequently, the cells remained in the stationary phase. The growth curve revealed the extremely strong vitality of the cells; the amplification efficiency curve of the 16s rRNA, ldh, ldhB, and ldhX genes indicated similar amplification efficiencies (close to 100%) of the reference and target genes. These results indicated that the fluorescence-based quantitative real time PCR method reflected the expression level of the target genes adequately. The ldh, ldhB, and ldhX genes were expressed to specific levels during the three time points (6 h, 9 h, and 12 h) of strain growth. In addition to the growth of the strain, the gene expression levels demonstrated a significant upward trend, with a continuous amplitude of increase; the highest expression level was observed at 12 h post-initiation. The levels of expression of the ldh gene significantly differed among the three time points; in addition, the expression of ldhB significantly differed from that of ldhX.
