Sporulation In Bacteria Research Articles

Peculiarities of the Ontogenesis of Bacilli During Development from a Vegetative Cell to a Spore

Understanding the development processes of bacteria, in particular spore-forming ones, has both fundamental and applied importance, since at various stages of this process, the cells of microorganisms perform certain functions that can be regulated by influencing certain factors depending on the tasks. Literature data and the results of our research on the influence of the composition of the nutrient medium, pH, temperature, and aeration on sporulation are analyzed in the article. It isshown that the direction of bacterial cells’ development in certain ways is determined by signals that come from the surrounding environment, affect their genome, and determine the ways of cell development – growth or sporulation. Sporogenesis can also be induced by metabolites formed during microorganism development. It is emphasized that the environmental factors that influence the sporulation of bacteria have been studied in sufficient detail. However, the mechanisms of their action remain debatable. Morphological, genetic, and biochemical changes of spore-forming bacteria under the conditions of macrocyclic and microcyclic ways of their development are also highlighted, which makes it possible to correctly understand the functioning of regulatory mechanisms in the ontogenesis of microbial cells. In particular, the data of our research on the dynamics of morphological changes in the ontogenesis of a specific individual bacterial cell are presented. In addition, factors, including specific terminal products of cell metabolism, such as antibiotics, and genetic mechanisms of sporogenesis regulation of various genera and species of bacteria are described in detail. The nature of the vast majority of "sporogenes" has not been clarified, and there are only a few hypotheses regarding the mechanism of their action. However, most of the biological regulators of sporogenesis were found in the culture liquid, which indicates the cellular nature of their action. Therefore, to obtain more convincing data on the regulation of sporogenesis, studies at the cellular level are needed.

Identification of serine/threonine kinases that regulate metabolism and sporulation in Clostridium beijerinckii.

Serine/threonine protein kinases (STKs) are important for signal transduction and involved in multiple physiological processes, including cell growth, central metabolism, and sporulation in bacteria. However, the role of STKs in solventogenic clostridia remains unclear. Here, we identified and comprehensively investigated six STK candidates in Clostridium beijerinckii. These STKs were classified into four groups with distinct characteristics via analysis of genetic organizations, prediction of protein domains, and multiple sequence alignment. Cbei0566 is a member of the PrkA family with 41% identity to PrkA from Bacillus subtilis, and both Cbei0666 and Cbei0813 are two-component-like STKs. Cbei1151 and Cbei1929 belong to the Hanks family STKs and consist of a cytoplasmic catalytic domain, a transmembrane region, and extracellular sensor domains. In-frame deletion mutants of cbei0566, cbei0666, cbei1929, and cbei2661 displayed similar cell growth with wild type. Both Δcbei0666 and Δcbei2661 improved acetone-butanol-ethanol (ABE) production by 14.3% (19.2g/L vs. 16.8g/L), and the sporulation frequencies of Δcbei0566, Δcbei1929, and Δcbei2661 significantly decreased to 35.5%, 55.1% and 44.8%, respectively. The restored phenotypes after genetic complementation demonstrated their direct link to STKs deletion. Remarkably, overexpressing cbei0566 contributed to 41.5% more spore formation and cbei1929 overexpression enhanced ABE production from 19.3 to 24.2g/L, along with 25% less acids. These results revealed that Cbei0566 and Cbei1929 had prominent regulatory functions. This study expands the current knowledge of the existence and functions of STKs in prokaryotes and highlights the importance of STK-mediated signaling networks in developing superior strains. KEY POINTS: • First reported serine/threonine protein kinases in solventogenic clostridia • Six STKs with distinct properties possessed diverse functions in C. beijerinckii • Cbei1929 and Cbei0566 remarkably regulated solventogenesis and sporulation.

Genetics: Location affects sporulation.

Monitored changes in the number of copies of a gene during DNA replication control the timing of sporulation in bacteria. This discovery links replication to the concept that a gene's location on a chromosome can influence cell traits.

A cell–cell communication system regulates protease production during sporulation in bacteria of the Bacillus cereus group

In sporulating Bacillus, major processes like virulence gene expression and sporulation are regulated by communication systems involving signalling peptides and regulators of the RNPP family. We investigated the role of one such regulator, NprR, in bacteria of the Bacillus cereus group. We show that NprR is a transcriptional regulator whose activity depends on the NprX signalling peptide. In association with NprX, NprR activates the transcription of an extracellular protease gene (nprA) during the first stage of the sporulation process. The transcription start site of the nprA gene has been identified and the minimal region necessary for full activation has been characterized by promoter mutagenesis. We demonstrate that the NprX peptide is secreted, processed and then reimported within the bacterial cell. Once inside the cell, the mature form of NprX, presumably the SKPDIVG heptapeptide, directly binds to NprR allowing nprA transcription. Alignment of available NprR sequences from different species of the B. cereus group defines seven NprR clusters associated with seven NprX heptapeptide classes. This cell-cell communication system was found to be strain-specific with a possible cross-talk between some pherotypes. The phylogenic relationship between NprR and NprX suggests a coevolution of the regulatory protein and its signalling peptide.

Formation of complex bacterial colonies via self-generated vortices.

Depending on the environmental conditions bacterial colonies growing on agar surfaces can exhibit complex colony formation and various types of collective motion. Experimental results are presented concerning the hydrodynamics (vortices, migration of bacteria in clusters) and colony formation of a morphotype of Bacillus subtilis. Some of these features are not specific to this morphotype but also have been observed in several other bacterial strains, suggesting the presence of universal effects. A simple model of self-propelled particles is proposed, which is capable of describing the hydrodynamics on the intermediate level, including the experimentally observed rotating disks of bacteria. The colony formation is captured by a complex generic model taking into account nutrient diffusion, reproduction, and sporulation of bacteria, extracellular slime deposition, chemoregulation, and inhomogeneous population. Our model also sheds light on some possible biological benefits of this ``multicellular behavior.'' \textcopyright{} 1996 The American Physical Society.

Regulation of the phosphorelay and the initiation of sporulation in Bacillus subtilis.

The initiation of sporulation of bacteria is a complex cellular event controlled by an extensive network of regulatory proteins that serve to ensure that a cell embarks on this differentiation process only when appropriate conditions are met. The major signal-transduction pathway for the initiation of sporulation is the phosphorelay, which responds to environmental, cell cycle, and metabolic signals, and phosphorylates the Spo0A transcription factor activating its function. Signal input into the phosphorelay occurs through activation of kinases to phosphorylate a secondary-messenger protein, Spo0F. Spo0F-P serves as a substrate for phosphoprotein phosphotransferase, Spo0B, which phosphorylates Spo0A. The pathway is regulated by transcriptional control of its component proteins and by regulating phosphate flux through the pathway. This is accomplished by several regulatory proteins, and by activated Spo0A, which regulates transcription of genes for its own synthesis. Spo0A-P indirectly controls the transcription of numerous genes by regulating the level of other transcription regulators and directly activates the transcription of several regulatory proteins and sigma factors required for progression to the second stage of sporulation. Although the pathway and regulatory proteins have been identified, the signals and effectors for these regulators remain a mystery.

An effective method of preparing sections of Bacillus polymyxa sporangia and spores for electron microscopy.

Bacillus polymyxa sporangia and spores were prepared for examination in the electron microscope by methods whose critical features were apparently: judicious use of vacuum, to encourage complete penetration of the embedding medium; the use of epoxy resins as embedding media; and cutting of the thin sections with a diamond knife. Electron micrographs of material prepared in this manner exhibit undeformed sporangial sections. Some of the structures revealed have been shown before, though perhaps less distinctly; other structures are revealed here for the first time. While this single study does not pretend to elucidate all the complexities of sporulation in bacteria, these and similar images should make this possible, and some mention of the preparatory techniques that lead to them seems advisable at this time.