| Arthrobacter species are one of the most frequently isolated Actinobacteria from soils. Arthrobacter have multiple functions, such as degradation of organic pollutants, biological nitrogen fixation, synthesis of biofuel and so on. Therefore, the strains of the genus Arthrobacter are valuable candidates in potential application. The environmental prevalence of Arthrobacter species may be due to its capability for long period survival under stressful conditions caused by starvation, temperature shifts, and etcetera. Arthrobacter cells have several different shapes, including rod, coccus, or myceloid, which might also have implications for their ability to resist stress conditions. Previous studies on the Arthrobacter are mainly about the degradation of organic pollutants and the genomic research. Due to the useful plasmid was reported in 2005, there is rare research on the cell division and development in Arthrobacter.In this research, we used several strategies, including sequencing and analysis of the complete genome, biochemistry and genetics experiments, to analyze the new cell division genes or the gene with new function to regulate the cell division of the Arthrobacter strain A3, which was isolated from a frozen soil from Tianshan Mountain, and the Arthrobacter strain Ar51, which was isolated from a frozen soil from Tibetan Plateau. Finally, we have got the following conclusions:1. The charge effect sensitivity of FtsZ is the key factor to regulate the morphology of Arthrobacter. Compared with the FtsZ from other bacteria, the FtsZ of Arthrobacter has novel functions to regulate the polymorphism of Arthrobacter. The characteristics of Arthrobacter FtsZ polymerization are as follows: Firstly, the polymerization of Arthrobacter FtsZ into filament is very sensitive to the charge effect. The stronger of charge effect, the weaker ability of polymerization into filament. Secondly, the polymerization rate of Arthrobacter FtsZ is very slow, as being compared with other bacteria. For the full polymerization, Arthrobacter FtsZ needs at least 1000 s, while 320 s is enough for the other bacterial strains. Thirdly, potassium is a necessary factor for the polymerization of Arthrobacter FtsZ into long filament. Analyzed the FtsZ location(strained by Van-flu) in the Arthrobacter, which has grown in the different salt concentrations, the Z-ring formation in the high salt medium is only 0-1 ring/strain and causing the strain form the myceloid growth. In the normal salt concentration, the Z-ring formation is 1 ring/strain and the morphology is the rod shape. However, the strain cannot grow in a very low salt concentration medium. Compared with other bacteria, the charge effect of FtsZ in Arthrobacter is a key factor to regulate the morphology change of this strain.2. sfi gene was responsible for the septum formation during the cell division. Using the CoIP method, we found a new protein in both strains, which closely related to the cell division of Arthrobacter. We call this gene as sfi. Compared with the wild type strain, the growth rate of the sfi knock out strain is very low. And the length of strain is shorter than that of the wild type strain. Additionally, the septum formation is always failed in the sfi knock out strain.3. FzpA, which can promote polymerization of FtsZ in vivo, is a wide distributed novel intermediate filament in Actinobacteria. In this research, we analyzed the intermediate filament like protein with high-throughput screening by Coil-Coil software in the Arthrobacter strain A3’s genome. After analyzed the biochemical characteristic, one of these proteins(we call it as FzpA) is a new intermediate filament protein, which can polymerize into network in vitro. It is lethal for the strain when fzpA has been knocked out. The growth rate of overexpression of FzpA strain is very low and contains 3 Z-ring per strain, while the wild type strain has only 1 Z-ring per strain. Using SMART to analyze the conserved domain of FzpA, we found that it contained an FtsZ binding domain, a ZipA binding domain, and a transmembrane domain. By analysis of the FzpA sequences, we found that FzpA were widely present in Actinobacteria. We supposed that the FzpA is a novel intermediate filament, which has the function to substitute the FtsA in Actinobacteria.In this research, we found two new genes, which have functions in cell division, and one of the genes has new function to regulate the cell division in the Arthrobacter strains A3 and Ar51. It is helpful for the research in the cell division of Actinobacteria. Additionally, the morphology changed, cell wall synthesis and cell division of Mycobacterium species are very similar to the Arthrobacter species. Therefore, the genetic nature of Arthrobacter development will help people to find new drugs to kill the Mycobacterium. |
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