Flexibility and constraint: Evolutionary remodeling of the sporulation initiation pathway in Firmicutes

AbstractBacteria that reside in the gastrointestinal tract of healthy humans are essential for our health, sustenance and well-being. About 50–60% of those bacteria have the ability to produce resilient spores that are important for the life cycle in the gut and for host-to-host transmission. A genomic signature for sporulation in the human intestine was recently described, which spans both commensals and pathogens such as Clostridioides difficile and contains several genes of unknown function. We report on the characterization of a signature gene, CD25890, which, as we show is involved in the control of sporulation initiation in C. difficile under certain nutritional conditions. Spo0A is the main regulatory protein controlling entry into sporulation and we show that an in-frame deletion of CD25890 results in increased expression of spo0A per cell and increased sporulation. The effect of CD25890 on spo0A is likely indirect and mediated through repression of the sinRR´ operon. Deletion of the CD25890 gene, however, does not alter the expression of the genes coding for the cytotoxins or the genes involved in biofilm formation. Our results suggest that CD25890 acts to modulate sporulation in response to the nutrients present in the environment.

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Sporulation in solventogenic and acetogenic clostridia

Applied Microbiology and Biotechnology ◽

10.1007/s00253-021-11289-9 ◽

2021 ◽

Author(s):

Mamou Diallo ◽

Servé W. M. Kengen ◽

Ana M. López-Contreras

Keyword(s):

Current Knowledge ◽

Carbon Sources ◽

Cost Effective ◽

Biotechnological Production ◽

Key Points ◽

Wide Range ◽

Potential Applications ◽

A Cell ◽

Sporulation Initiation ◽

Solventogenic Clostridia

AbstractThe Clostridium genus harbors compelling organisms for biotechnological production processes; while acetogenic clostridia can fix C1-compounds to produce acetate and ethanol, solventogenic clostridia can utilize a wide range of carbon sources to produce commercially valuable carboxylic acids, alcohols, and ketones by fermentation. Despite their potential, the conversion by these bacteria of carbohydrates or C1 compounds to alcohols is not cost-effective enough to result in economically viable processes. Engineering solventogenic clostridia by impairing sporulation is one of the investigated approaches to improve solvent productivity. Sporulation is a cell differentiation process triggered in bacteria in response to exposure to environmental stressors. The generated spores are metabolically inactive but resistant to harsh conditions (UV, chemicals, heat, oxygen). In Firmicutes, sporulation has been mainly studied in bacilli and pathogenic clostridia, and our knowledge of sporulation in solvent-producing or acetogenic clostridia is limited. Still, sporulation is an integral part of the cellular physiology of clostridia; thus, understanding the regulation of sporulation and its connection to solvent production may give clues to improve the performance of solventogenic clostridia. This review aims to provide an overview of the triggers, characteristics, and regulatory mechanism of sporulation in solventogenic clostridia. Those are further compared to the current knowledge on sporulation in the industrially relevant acetogenic clostridia. Finally, the potential applications of spores for process improvement are discussed.Key Points• The regulatory network governing sporulation initiation varies in solventogenic clostridia.• Media composition and cell density are the main triggers of sporulation.• Spores can be used to improve the fermentation process.

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Differential Processing of Propeptide Inhibitors of Rap Phosphatases in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.182.2.303-310.2000 ◽

2000 ◽

Vol 182 (2) ◽

pp. 303-310 ◽

Cited By ~ 109

Author(s):

Min Jiang ◽

Roberto Grau ◽

Marta Perego

Keyword(s):

Bacillus Subtilis ◽

Phosphatase Activity ◽

Response Regulators ◽

Histidine Kinases ◽

Physiological Processes ◽

Carboxy Terminal Domain ◽

Activation Level ◽

Sporulation Initiation ◽

Carboxy Terminal

ABSTRACT In the phosphorelay signal transduction system for sporulation initiation in Bacillus subtilis, the opposing activities of histidine kinases and aspartyl phosphate phosphatases determine the cell's decision whether to continue with vegetative growth or to initiate the differentiation process. Regulated dephosphorylation of the Spo0A and Spo0F response regulators allows a variety of negative signals from physiological processes that are antithetical to sporulation to impact on the activation level of the phosphorelay. Spo0F∼P is the known target of two related phosphatases, RapA and RapB. In addition to RapA and RapB, a third member of the Rap family of phosphatases, RapE, specifically dephosphorylated the Spo0F∼P intermediate in response to competence development. RapE phosphatase activity was found to be controlled by a pentapeptide (SRNVT) generated from within the carboxy-terminal domain of the phrE gene product. A synthetic PhrE pentapeptide could (i) complement the sporulation deficiency caused by deregulated RapE activity of aphrE mutant and (ii) inhibit RapE-dependent dephosphorylation of Spo0F∼P in in vitro experiments. The PhrE pentapeptide did not inhibit the phosphatase activity of RapA and RapB. These results confirm previous conclusions that the specificity for recognition of the target phosphatase is contained within the amino acid sequence of the pentapeptide inhibitor.

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Genetic mechanisms governing sporulation initiation in Clostridioides difficile

Current Opinion in Microbiology ◽

10.1016/j.mib.2021.12.001 ◽

2022 ◽

Vol 66 ◽

pp. 32-38

Author(s):

Cheyenne D Lee ◽

Arshad Rizvi ◽

Adrianne N Edwards ◽

Michael A DiCandia ◽

Germán G Vargas Cuebas ◽

...

Keyword(s):

Clostridioides Difficile ◽

Genetic Mechanisms ◽

Sporulation Initiation

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Artificial Sporulation Induction (ASI) by kinA Overexpression Affects the Proteomes and Properties of Bacillus subtilis Spores

International Journal of Molecular Sciences ◽

10.3390/ijms21124315 ◽

2020 ◽

Vol 21 (12) ◽

pp. 4315

Author(s):

Zhiwei Tu ◽

Wishwas R. Abhyankar ◽

Bhagyashree N. Swarge ◽

Nicole van der Wel ◽

Gertjan Kramer ◽

...

Keyword(s):

Proteome Analysis ◽

Spore Formation ◽

Single Spore ◽

Coping With Stress ◽

Carbon And Nitrogen ◽

Spore Yield ◽

Wet Heat ◽

Carbon And Nitrogen Metabolism ◽

Sporulation Initiation ◽

Set Up

To facilitate more accurate spore proteomic analysis, the current study focuses on inducing homogeneous sporulation by overexpressing kinA and assesses the effect of synchronized sporulation initiation on spore resistance, structures, the germination behavior at single-spore level and the proteome. The results indicate that, in our set up, the sporulation by overexpressing kinA can generate a spore yield of 70% within 8 h. The procedure increases spore wet heat resistance and thickness of the spore coat and cortex layers, whilst delaying the time to spore phase-darkening and burst after addition of germinant. The proteome analysis reveals that the upregulated proteins in the kinA induced spores, compared to spores without kinA induction, as well as the ‘wildtype’ spores, are mostly involved in spore formation. The downregulated proteins mostly belong to the categories of coping with stress, carbon and nitrogen metabolism, as well as the regulation of sporulation. Thus, while kinA overexpression enhances synchronicity in sporulation initiation, it also has profound effects on the central equilibrium of spore formation and spore germination, through modulation of the spore molecular composition and stress resistance physiology.

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Asexual Sporulation in Aspergillus nidulans

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.62.1.35-54.1998 ◽

1998 ◽

Vol 62 (1) ◽

pp. 35-54 ◽

Cited By ~ 479

Author(s):

Thomas H. Adams ◽

Jenny K. Wieser ◽

Jae-Hyuk Yu

Keyword(s):

Life Cycle ◽

Aspergillus Nidulans ◽

Reproductive Mode ◽

Fungal Species ◽

Intrinsic Signals ◽

Regulatory Interactions ◽

Asexual Sporulation ◽

Extracellular Signal ◽

Sporulation Initiation ◽

Fungal Life Cycle

SUMMARY The formation of mitotically derived spores, called conidia, is a common reproductive mode in filamentous fungi, particularly among the large fungal class Ascomycetes. Asexual sporulation strategies are nearly as varied as fungal species; however, the formation of conidiophores, specialized multicellular reproductive structures, by the filamentous fungus Aspergillus nidulans has emerged as the leading model for understanding the mechanisms that control fungal sporulation. Initiation of A. nidulans conidipohore formation can occur either as a programmed event in the life cycle in response to intrinsic signals or to environmental stresses such as nutrient deprivation. In either case, a development-specific set of transcription factors is activated and these control the expression of each other as well as genes required for conidiophore morphogenesis. Recent progress has identified many of the earliest-acting genes needed for initiating conidiophore development and shown that there are at least two antagonistic signaling pathways that control this process. One pathway is modulated by a heterotrimeric G protein that when activated stimulates growth and represses both asexual and sexual sporulation as well as production of the toxic secondary metabolite, sterigmatocystin. The second pathway apparently requires an extracellular signal to induce sporulation-specific events and to direct the inactivation of the first pathway, removing developmental repression. A working model is presented in which the regulatory interactions between these two pathways during the fungal life cycle determine whether cells grow or develop.

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