Journal of Microbiology

Research Support, Non-U.S. Gov't

Evaluation of the Cell Growth of Mycobacteria Using Mycobacterium smegmatis mc2 155 as a Representative Species: Jorge A. Gonzalez-y-Merchand , Ruben Zaragoza-Contreras , Rosalina Guadarrama-Medina , Addy C. Helguera-Repetto , Sandra Rivera-Gutierrez , Jorge F. Cerna-Cortes , Leopoldo Santos-Argumedo , Robert A. Cox; J. Microbiol. 2012;50(3):419-425. Published online June 30, 2012; DOI: https://doi.org/10.1007/s12275-012-1556-0

Abstract: The study of the in vitro cell growth of mycobacteria still remains a fastidious, difficult, and time-consuming procedure. In addition, assessing mycobacterial growth in the laboratory is often complicated by cell aggregation and slow growth-rate. We now report that the use of a stainless steel spring in the culture led to an absence of large cell clumps, to a decrease of dead cells in the exponential phase and to growth of a more homogeneous population of large cells. We also report that flow cytometry is a rapid, simple and reliable approach to monitor mycobacterial cell growth and viability. Here, we monitored Mycobacterium smegmatis cellular growth by optical density, dry cell mass, and colony forming units; in addition, viability, cell size and granularity profiles were analyzed by flow cytometry, and cell morphology by electron microscopy. Cultures monitored by flow cytometry may lead to a better understanding of the physiology of mycobacteria. Moreover, this methodology may aid in characterizing the cell growth of other fastidious species of microorganisms.

Reversible function of RapA with the C-terminus of RapC in Dictyostelium: Dongju Kim , Wonbum Kim , Taeck Joong Jeon; J. Microbiol. 2021;59(9):853-848.; DOI: https://doi.org/10.1007/s12275-021-1400-5

Abstract: Rap small GTPases are involved in diverse signaling pathways associated with cell growth, proliferation, and cell migration. There are three Rap proteins in Dictyostelium, RapA, RapB, and RapC. RapA is a key regulator in the control of cell adhesion and migration. Recently RapA and RapC have been reported to have opposite functions in the regulation of cellular processes. In this study, we demonstrate that the C-terminus of RapC, which is not found in RapA, is essential for the opposite functions of RapC and is able to reverse the functions of RapA when fused to the tail of RapA. Cells lacking RapC displayed several defective phenotypes, including spread morphology, strong adhesion, and decreased cell migration compared to wild-type cells. These phenotypes were rescued by full-length RapC, but not by RapC missing the C-terminus. Furthermore, recombinant RapA fused with the C-terminus of RapC completely recovered the phenotypes of rapC null cells, indicating that the functions of RapA were modified to become similar to those of RapC by the C-terminus of RapC with respect to cell morphology, cell adhesion and migration, cytokinesis, and development. These results suggest that the C-terminal residues of RapC are able to suppress and change the functions of other Ras proteins in Ras oncogenic signaling pathways.

Search