Arginine methylation helps SepIVA balance regulation of septation and elongation in Mycobacterium smegmatis

Growth of mycobacterial cells requires successful coordination between elongation and division of the cell wall. However, it is not clear which factors directly mediate this coordination. Here, we studied the function and post-translational modification of an essential division factor, SepIVA, in Mycobacterium smegmatis. We find that SepIVA is arginine methylated, and that these modifications alter both division and polar elongation of Msmeg. Furthermore, SepIVA impacts the localization of MurG. Polar localization of MurG correlates with polar elongation in arginine methylation mutants of sepIVA. These results establish SepIVA as a regulator of both elongation and division, and characterize a physiological role for protein arginine methylation for the first time in bacteria.

Ultimate effect of non-identity of capacitive elements of high-voltage arm on frequency characteristics of voltage divider (analytical research)

Purpose. Determination in the analytical form of the maximum limiting influence of the non-identity of the capacitive elements of the high-voltage arm on the amplitude-frequency characteristic and phase-frequency characteristic of the voltage divider with parallel-series connection of R-, C-elements of the high-voltage arm. Methodology. Based on the previously developed theory of broadband voltage dividers with parallel-series connection of R-, C-elements, analytical expressions for amplitude-frequency and phase-frequency characteristics of the voltage divider are obtained and investigated taking into account the limit case of non-identical capacitive elements of high-voltage arm. Results. The nature of the dependencies of the frequency characteristics of the broadband voltage divider on the value of the tolerance of the capacitive elements of the high-voltage arm, the division factor of the voltage divider in a wide range of frequency changes is determined. Simplified approximating expressions for the maximum values of frequency characteristics of the voltage divider are proposed and their error is determined. Originality. For the first time in the analytical form the limiting influence of non-identity of capacitive elements of a high-voltage arm of a voltage divider on its frequency characteristics is considered. A mathematical model of this influence is constructed and the limit values of frequency characteristics of the voltage divider are determined. Practical value. It is recommended to introduce into the normative documentation of broadband voltage dividers the corrected value of the division factor, which allows to significantly reduce the deviation of the actual value of the division factor of the voltage divider from the normalized value in a wide range of frequency changes.

Casein kinase TbCK1.2 regulates division of kinetoplast DNA, and movement of basal bodies in the African trypanosome

The single mitochondrial nucleoid (kinetoplast) of Trypanosoma brucei is found proximal to a basal body (mature (mBB)/probasal body (pBB) pair). Kinetoplast inheritance requires synthesis of, and scission of kinetoplast DNA (kDNA) generating two kinetoplasts that segregate with basal bodies into daughter cells. Molecular details of kinetoplast scission and the extent to which basal body separation influences the process are unavailable. To address this topic, we followed basal body movements in bloodstream trypanosomes following depletion of protein kinase TbCK1.2 which promotes kinetoplast division. In control cells we found that pBBs are positioned 0.4 um from mBBs in G1, and they mature after separating from mBBs by at least 0.8 um: mBB separation reaches ~2.2 um. These data indicate that current models of basal body biogenesis in which pBBs mature in close proximity to mBBs may need to be revisited. Knockdown of TbCK1.2 produced trypanosomes containing one kinetoplast and two nuclei (1K2N), increased the percentage of cells with uncleaved kDNA 400%, decreased mBB spacing by 15%, and inhibited cytokinesis 300%. We conclude that (a) separation of mBBs beyond a threshold of 1.8 um correlates with division of kDNA, and (b) TbCK1.2 regulates kDNA scission. We propose a Kinetoplast Division Factor hypothesis that integrates these data into a pathway for biogenesis of two daughter mitochondrial nucleoids.

The cell division factor ZapB is required for bile resistance in Salmonella enterica

ABSTRACTA gene annotated as yiiU in the genome of Salmonella enterica serovar Typhimurium encodes a protein homologous to E. coli ZapB, a non-essential cell division factor involved in Z-ring assembly. ZapB− null mutants of S. enterica are bile-sensitive. The ZapB protein is degraded in the presence of sodium deoxycholate (DOC), and degradation appears to involve the Lon protease. The amount of zapB mRNA increases in the presence of a sublethal concentration of DOC. This increase is not caused by upregulation of zapB transcription but by increased stability of zapB mRNA. DOC-induced increase of the zapB transcript is suppressed by an hfq mutation, suggesting the involvement of a small regulatory RNA. We provide evidence that such sRNA is MicA. Increased stability of zapB mRNA in the presence of DOC may counter degradation of bile-damaged ZapB, thus providing sufficient level of functional ZapB protein to permit Z-ring assembly in the presence of bile.IMPORTANCEBile salts have bactericidal activity as a consequence of membrane disruption, protein denaturation and DNA damage. However, intestinal bacteria are resistant to bile. Envelope structures such as the lipopolysaccharide and the enterobacterial common antigen act as barriers that reduce intake of bile salts. Remodelling of the outer membrane and the peptidoglycan, activation of efflux pumps, and upregulation of stress responses also contribute to bile resistance. This study adds the cell division factor ZapB (and presumably the Z-ring) to the list of cellular functions involved in bile resistance.

A Frequency Multiplier Based on Time Recursive Processing

This paper describes a digital frequency multiplier for a pulse rate. The multiplier is based on the recursive processing of the input and output periods and their time differences. Special emphasis is devoted to the techniques which provide the development of multipliers based on this principle. The circuit is defined by two system parameters. One is the ratio of two clock frequencies and the other is a division factor of a binary counter. The realization of the circuit is described. The region of the system parameters for the stable circuit is presented. The different aspects of applications and limitations in realization of the circuit are considered. All mathematical analyses are made using a Z transform approach. It is shown that the circuit can be also used in tracking and prediction applications. Computer simulations are performed to prove the correctness of the math and the whole approach.