title: Bacterial colony from two-dimensional division to three-dimensional development.
abstract: On agar surface, bacterial daughter cells form a 4-cell array after the first two rounds of division, and this phenomenon has been previously attributed to a balancing of interactions among the daughter bacteria and the underneath agar. We studied further the organization and development of colony after additional generations. By confocal laser scanning microscopy and real-time imaging, we observed that bacterial cells were able to self-organize and resulted in a near circular micro-colony consisting of monolayer cells. After continuous dividing, bacteria transited from two-dimensional expansion into three-dimensional growth and formed two to multi-layers in the center but retained a monolayer in the outer ring of the circular colony. The transverse width of this outer ring appeared to be approximately constant once the micro-colony reached a certain age. This observation supports the notion that balanced interplays of the forces involved lead to a gross morphology as the bacteria divide into offspring on agar surface. In this case, the result is due to a balance between the expansion force of the dividing bacteria, the non-covalent force among bacterial offspring and that between bacteria and substratum.
authors.affiliation: Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: Pin-Tzu
authors.initials: PT
authors.lastname: Su
authors.forename: Chih-Tang
authors.initials: CT
authors.lastname: Liao
authors.forename: Jiunn-Ren
authors.initials: JR
authors.lastname: Roan
authors.forename: Shao-Hung
authors.initials: SH
authors.lastname: Wang
authors.forename: Arthur
authors.initials: A
authors.lastname: Chiou
authors.forename: Wan-Jr
authors.initials: WJ
authors.lastname: Syu
mesh_terms: D000362:Agar; D002455:Cell Division / Q000502:physiology*; D004926:Escherichia coli / Q000254:growth & development*; D018613:Microscopy, Confocal
chemical_list: D000362:Agar