The divisome is a self-enhancing machine in Escherichia coli and Caulobacter crescentus.

During bacterial cytokinesis, polymers of the bacterial tubulin FtsZ coalesce into the Z ring to orchestrate divisome assembly and septal cell wall synthesis. Previous studies have found that Z ring condensation and stability is critical for successful cell division. However, how FtsZ filaments condense into a Z ring remains enigmatic and whether septal cell wall synthesis can feedback to the Z ring has not been investigated.

Widespread photosynthesis reaction centre barrel proteins are necessary for haloarchaeal cell division.

Cell division is fundamental to all cellular life. Most archaea depend on either the prokaryotic tubulin homologue FtsZ or the endosomal sorting complex required for transport for division but neither system has been robustly characterized. Here, we show that three of the four photosynthesis reaction centre barrel domain proteins of Haloferax volcanii (renamed cell division proteins B1/2/3 (CdpB1/2/3)) play important roles in cell division.

Isolation, functional evaluation, and fermentation process optimization of probiotic Bacillus coagulans.

Bacillus coagulans is a probiotic agent widely used in various industries. In this study, we isolated a novel strain of B. coagulans, X26, from soil and characterized its properties.

ICTV Virus Taxonomy Profile: 2023.

The family includes tailless icosahedral viruses with an internal lipid membrane. The capsid is constructed from two major capsid proteins, both with a single jelly-roll fold. The genome is a circular dsDNA molecule of 16-19 kb.

Widespread PRC barrel proteins play critical roles in archaeal cell division.

Cell division is fundamental to all cellular life. Most of the archaea employ one of two alternative division machineries, one centered around the prokaryotic tubulin homolog FtsZ and the other around the endosomal sorting complex required for transport (ESCRT). However, neither of these mechanisms has been thoroughly characterized in archaea.

ICTV Virus Taxonomy Profile: 2023.

Members of the family have non-enveloped tailless icosahedral virions with a protein-rich internal lipid membrane. The genome is a linear double-stranded DNA of about 30 kbp with inverted terminal repeats and terminal proteins. The capsid has a pseudo triangulation 28 symmetry and is built of two major capsid protein types.

Cell-to-cell natural transformation in Bacillus subtilis facilitates large scale of genomic exchanges and the transfer of long continuous DNA regions.

Natural transformation is one of the major mechanisms of horizontal gene transfer. Although it is usually studied using purified DNA in the laboratory, recent studies showed that many naturally competent bacteria acquired exogenous DNA from neighboring donor cells. Our previous work indicates that cell-to-cell natural transformation (CTCNT) using two different Bacillus subtilis strains is a highly efficient process; however, the mechanism is unclear.

A virus-borne DNA damage signaling pathway controls the lysogeny-induction switch in a group of temperate pleolipoviruses.

Many prokaryotic viruses are temperate and their reactivation is tightly regulated. However, except for a few bacterial model systems, the regulatory circuits underlying the exit from lysogeny are poorly understood, especially in archaea. Here, we report a three-gene module which regulates the switch between lysogeny and replicative cycle in a haloarchaeal virus SNJ2 (family Pleolipoviridae).

Tankyrases inhibit innate antiviral response by PARylating VISA/MAVS and priming it for RNF146-mediated ubiquitination and degradation.

During viral infection, sensing of viral RNA by retinoic acid-inducible gene-I-like receptors (RLRs) initiates an antiviral innate immune response, which is mediated by the mitochondrial adaptor protein VISA (virus-induced signal adaptor; also known as mitochondrial antiviral signaling protein [MAVS]). VISA is regulated by various posttranslational modifications (PTMs), such as polyubiquitination, phosphorylation, -linked β-d--acetylglucosaminylation (O-GlcNAcylation), and monomethylation. However, whether other forms of PTMs regulate VISA-mediated innate immune signaling remains elusive.

Identification of the potential active site of the septal peptidoglycan polymerase FtsW.

SEDS (Shape, Elongation, Division and Sporulation) proteins are widely conserved peptidoglycan (PG) glycosyltransferases that form complexes with class B penicillin-binding proteins (bPBPs, with transpeptidase activity) to synthesize PG during bacterial cell growth and division. Because of their crucial roles in bacterial morphogenesis, SEDS proteins are one of the most promising targets for the development of new antibiotics. However, how SEDS proteins recognize their substrate lipid II, the building block of the PG layer, and polymerize it into glycan strands is still not clear.

FtsA acts through FtsW to promote cell wall synthesis during cell division in .

In , FtsQLB is required to recruit the essential septal peptidoglycan (sPG) synthase FtsWI to FtsA, which tethers FtsZ filaments to the membrane. The arrival of FtsN switches FtsQLB in the periplasm and FtsA in the cytoplasm from a recruitment role to active forms that synergize to activate FtsWI. Genetic evidence indicates that the active form of FtsQLB has an altered conformation with an exposed domain of FtsL that acts on FtsI to activate FtsW.

Bacterial Viruses Subcommittee and Archaeal Viruses Subcommittee of the ICTV: update of taxonomy changes in 2021.

In this article, we - the Bacterial Viruses Subcommittee and the Archaeal Viruses Subcommittee of the International Committee on Taxonomy of Viruses (ICTV) - summarise the results of our activities for the period March 2020 - March 2021. We report the division of the former Bacterial and Archaeal Viruses Subcommittee in two separate Subcommittees, welcome new members, a new Subcommittee Chair and Vice Chair, and give an overview of the new taxa that were proposed in 2020, approved by the Executive Committee and ratified by vote in 2021. In particular, a new realm, three orders, 15 families, 31 subfamilies, 734 genera and 1845 species were newly created or redefined (moved/promoted).

Genetic analysis of the septal peptidoglycan synthase FtsWI complex supports a conserved activation mechanism for SEDS-bPBP complexes.

SEDS family peptidoglycan (PG) glycosyltransferases, RodA and FtsW, require their cognate transpeptidases PBP2 and FtsI (class B penicillin binding proteins) to synthesize PG along the cell cylinder and at the septum, respectively. The activities of these SEDS-bPBPs complexes are tightly regulated to ensure proper cell elongation and division. In Escherichia coli FtsN switches FtsA and FtsQLB to the active forms that synergize to stimulate FtsWI, but the exact mechanism is not well understood.

Essential Role for FtsL in Activation of Septal Peptidoglycan Synthesis.

Spatiotemporal regulation of septal peptidoglycan (PG) synthesis is achieved by coupling assembly and activation of the synthetic enzymes (FtsWI) to the Z ring, a cytoskeletal element that is required for division in most bacteria. In , the recruitment of the FtsWI complex is dependent upon the cytoplasmic domain of FtsL, a component of the conserved FtsQLB complex. Once assembled, FtsWI is activated by the arrival of FtsN, which acts through FtsQLB and FtsA, which are also essential for their recruitment.

Roles of ATP Hydrolysis by FtsEX and Interaction with FtsA in Regulation of Septal Peptidoglycan Synthesis and Hydrolysis.

In , FtsEX coordinates peptidoglycan (PG) synthesis and hydrolysis at the septum. It acts on FtsA in the cytoplasm to promote recruitment of septal PG synthetases and recruits EnvC, an activator of septal PG hydrolases, in the periplasm. Following recruitment, ATP hydrolysis by FtsEX is thought to regulate both PG synthesis and hydrolysis, but how it does this is not well understood.

ORF4 of the Temperate Archaeal Virus SNJ1 Governs the Lysis-Lysogeny Switch and Superinfection Immunity.

Recent environmental and metagenomic studies have considerably increased the repertoire of archaeal viruses and suggested that they play important roles in nutrient cycling in the biosphere. However, very little is known about how they regulate their life cycles and interact with their hosts. Here, we report that the life cycle of the temperate haloarchaeal virus SNJ1 is controlled by the product ORF4, a small protein belonging to the antitoxin MazE superfamily.

Roles of FtsEX in cell division.

FtsEX is a member of a small subclass of ABC transporters that uses mechano-transmission to perform work in the periplasm. FtsEX controls periplasmic peptidoglycan (PG) hydrolase activities in many Gram negative and positive organisms to ensure the safe separation of daughter cells during division. In these organisms FtsEX localizes to the Z ring and uses its ATPase activity to regulate its periplasmic effectors.

How FtsEX localizes to the Z ring and interacts with FtsA to regulate cell division.

In Escherichia coli, FtsEX, a member of the ABC transporter superfamily, is involved in regulating the assembly and activation of the divisome to couple cell wall synthesis to cell wall hydrolysis at the septum. Genetic studies indicate FtsEX acts on FtsA to begin the recruitment of the downstream division proteins but blocks septal PG synthesis until a signal is received that divisome assembly is complete. However, the details of how FtsEX localizes to the Z ring and how it interacts with FtsA are not clear.

At the Heart of Bacterial Cytokinesis: The Z Ring.

Bacterial cell division is mediated by the divisome which is organized by the Z ring, a cytoskeletal element formed by the polymerization of the tubulin homologue FtsZ. Despite billions of years of bacterial evolution, the Z ring is nearly universal among bacteria that have a cell wall and divide by binary fission. Recent studies have revealed the mechanism of cooperative assembly of FtsZ and that the Z ring consists of patches of FtsZ filaments tethered to the membrane that treadmill to distribute the septal biosynthetic machinery.

Prophage LambdaSo uses replication interference to suppress reproduction of coexisting temperate phage MuSo2 in Shewanella oneidensis MR-1.

Many bacterial genomes carry multiple prophages that compete with each other, potentially affecting the physiology, fitness, and pathogenicity of their hosts. However, molecular mechanisms of such prophage-prophage conflicts remain poorly understood. The genome of Shewanella oneidensis MR-1, a Gammaproteobacterium residing in aquatic environments and notable for its ability to reduce metal ions, harbours four prophages, two of which (LambdaSo and MuSo2) form infectious virions during biofilm formation.

4-Hydroxyphenylpyruvate Dioxygenase Thermolability Is Responsible for Temperature-Dependent Melanogenesis in Aeromonas salmonicida subsp. .

subsp. is a major pathogen affecting fisheries worldwide and is a well-known pigmented member of the genus. This subspecies produces melanin at ≤22°C.

FtsZ filaments have the opposite kinetic polarity of microtubules.

FtsZ is the ancestral homolog of tubulin and assembles into the Z ring that organizes the division machinery to drive cell division in most bacteria. In contrast to tubulin that assembles into 13 stranded microtubules that undergo dynamic instability, FtsZ assembles into single-stranded filaments that treadmill to distribute the peptidoglycan synthetic machinery at the septum. Here, using longitudinal interface mutants of FtsZ, we demonstrate that the kinetic polarity of FtsZ filaments is opposite to that of microtubules.

Disruption of divisome assembly rescued by FtsN-FtsA interaction in .

Cell division requires the assembly of a protein complex called the divisome. The divisome assembles in a hierarchical manner, with FtsA functioning as a hub to connect the Z-ring with the rest of the divisome and FtsN arriving last to activate the machine to synthesize peptidoglycan. FtsEX arrives as the Z-ring forms and acts on FtsA to initiate recruitment of the other divisome components.

MinC and FtsZ mutant analysis provides insight into MinC/MinD-mediated Z ring disassembly.

The Min system negatively regulates the position of the Z ring, which serves as a scaffold for the divisome that mediates bacterial cytokinesis. In , this system consists of MinC, which antagonizes assembly of the tubulin homologue FtsZ. MinC is recruited to the membrane by MinD and induced by MinE to oscillate between the cell poles.

E. coli Cell Cycle Machinery.

Cytokinesis in E. coli is organized by a cytoskeletal element designated the Z ring. The Z ring is formed at midcell by the coalescence of FtsZ filaments tethered to the membrane by interaction of FtsZ's conserved C-terminal peptide (CCTP) with two membrane-associated proteins, FtsA and ZipA.