Major microbiology research areas and techniques: cell division, cytoskeleton, stationary-phase and bioluminescence.

Abstract

This issue is the second part of our special series on recent insights into microbial physiology. This part explores advancements in established aspects of microbial physiology such as cell division and bioluminescence, but also highlights recent discoveries of the presence of cytoskeletal elements and a master stress regulator in bacterial cells. The articles in this part further confirm the usefulness of molecular techniques in advancing knowledge in microbial physiology and emphasize aspects we raised in our introduction to the first part of this series (1). For instance, the first article describes interesting discoveries on cell division, a process that was envisaged as a simple one in the early days of microbial physiology. Khattar and his colleagues (2) start with an interesting argument made by a prominent expert in this field indicating that molecular techniques have advanced our knowledge of cell division, but also raised ambiguities and showed that our current knowledge about this central mechanism is probably limited. This article demonstrates the presence of certain proteins and mechanisms mediating cell division, including the striking ring structure formed by the FtsZ gene product. The authors provide an informative description of these proteins and their role in the formation of the so-called divisome and the relation of this to the morphogenesis phenomenon in the model Gramnegative organism Escherichia coli. The second article also confirms what had been indicated in the previous issue (1) of how limited is the view of bacterial cells as being simple structures and just containers of enzymes. Here, Madkour and Mayer (3) report on the presence of cytoskeletal elements in a number of bacterial species. In addition to the prime function of these cytoskeletal elements in shaping cells, they are shown to be involved in central physiological mechanisms including cell division, chromosome segregation and cell motility. Interestingly, bacterial cytoskeletons were found to involve homologs of eukaryotic cytoskeletal proteins, but they also involve unique cytoskeletal elements that have not been detected in eukaryotic cells. This could be a reflection of additional functions, beside the basic structural one, that bacterial cytoskeletons can serve in the prokaryotic cell. The authors provide us with an enjoyable description of examples of cytoskeletons and their prospective roles in interesting species of bacteria. They also show the usefulness of such basic knowledge in microbial physiology to the biotechnology and drug discovery fields. The third article (4) is another example of how the research area of bacterial stress response is evolving and capturing interest in microbial physiology. It is interesting to note that the concept of stress response was first reported in humans, where the Austrian Doctor Hans Selye started to develop his theory of stress adaptation in 1926. He thought that patients develop a general adaptation syndrome (GAS) to cope with the stress of being ill. Not only humans, but also bacteria are shown to switch on diverse adaptive mechanisms to keep growing or surviving during stress. The present article (4) is written by the group who pioneered work on the central stress regulator RpoS in E. coli. This is an alternative RNA polymerase sigma factor protein that mediates the expression of several stress-responsive genes. Since its discovery in the 1990s, several lines of evidence are accumulating to show the importance of RpoS for cell survival during the stationary phase and exposure to stress. Yet, it has been shown that there are other important RpoS-independent genes that also aid cell survival under adverse conditions, e.g. ribosome modulation factor (5-7). In this article, Hengge and her co-workers describe how such a regulator is regulated! They report interesting discoveries that show how complicated and orchestrated is RpoS regulation at the cellular level, a view that is striking within the context of the pleiotropic effects of stress on cell physiology. …