title: In situ examination of cell growth and death of Lactococcus lactis.
abstract: This study enables in situ studying of the growth and death of a large number of individual cells in a solid matrix. A wild type of Lactococcus lactis and several mutants with varying expression of GuaB was investigated. Large variability in the final size of individual microcolonies arising from clonal cells was observed. However, when growth was averaged over 16 locations in a specimen, the SEM was small and notable differences could be observed between the investigated strains, where mutants with lower expression of GuaB had a slower growth rate. The results show that the slow-growing mutants exhibited a lower fraction of dead cells, which indicate that slow-growing mutants are slightly more robust than the faster-growing strains. The large variability in the final size of individual microcolonies arising from clonal cells was quite surprising. We suggest that the control of the size of a microcolony is, at least partially, related to the actual microcolony depended on phenotypic heterogeneity. These findings are important to consider whenever a solid medium with discrete microcolonies is investigated.
authors.affiliation: Department of Food Science, Food Microbiology, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Mia
authors.initials: M
authors.lastname: Ryssel
authors.forename: Zhi
authors.initials: Z
authors.lastname: Duan
authors.forename: Henrik
authors.initials: H
authors.lastname: Siegumfeldt
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D003470:Culture Media / Q000737:chemistry; D015870:Gene Expression; D014644:Genetic Variation; D007091:Image Processing, Computer-Assisted; D013294:Lactococcus lactis / Q000254:growth & development / Q000502:physiology*; D050296:Microbial Viability; D008853:Microscopy; D050505:Mutant Proteins / Q000096:biosynthesis / Q000235:genetics; D010641:Phenotype
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D050505:Mutant Proteins