title: Impact of aeration and heme-activated respiration on Lactococcus lactis gene expression: identification of a heme-responsive operon.
abstract: Lactococcus lactis is a widely used food bacterium mainly characterized for its fermentation metabolism. However, this species undergoes a metabolic shift to respiration when heme is added to an aerobic medium. Respiration results in markedly improved biomass and survival compared to fermentation. Whole-genome microarrays were used to assess changes in L. lactis expression under aerobic and respiratory conditions compared to static growth, i.e., nonaerated. We observed the following. (i) Stress response genes were affected mainly by aerobic fermentation. This result underscores the differences between aerobic fermentation and respiration environments and confirms that respiration growth alleviates oxidative stress. (ii) Functions essential for respiratory metabolism, e.g., genes encoding cytochrome bd oxidase, menaquinone biosynthesis, and heme uptake, are similarly expressed under the three conditions. This indicates that cells are prepared for respiration once O(2) and heme become available. (iii) Expression of only 11 genes distinguishes respiration from both aerobic and static fermentation cultures. Among them, the genes comprising the putative ygfCBA operon are strongly induced by heme regardless of respiration, thus identifying the first heme-responsive operon in lactococci. We give experimental evidence that the ygfCBA genes are involved in heme homeostasis.
authors.affiliation: Department of Physiology, Chr Hansen A/S, DK-2970 Hørsholm, Denmark. dkmbp@chr-hansen.com
authors.forename: Martin Bastian
authors.initials: MB
authors.lastname: Pedersen
authors.forename: Christel
authors.initials: C
authors.lastname: Garrigues
authors.forename: Karine
authors.initials: K
authors.lastname: Tuphile
authors.forename: Célia
authors.initials: C
authors.lastname: Brun
authors.forename: Karin
authors.initials: K
authors.lastname: Vido
authors.forename: Mads
authors.initials: M
authors.lastname: Bennedsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Møllgaard
authors.forename: Philippe
authors.initials: P
authors.lastname: Gaudu
authors.forename: Alexandra
authors.initials: A
authors.lastname: Gruss
mesh_terms: D000332:Aerobiosis; D019677:Artificial Gene Fusion; D015152:Blotting, Northern; D005285:Fermentation; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D017930:Genes, Reporter; D006418:Heme / Q000378:metabolism*; D013294:Lactococcus lactis / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D009876:Operon; D018384:Oxidative Stress; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D006418:Heme; D001616:beta-Galactosidase