Clostridioides difficile Phosphoproteomics Shows an Expansion of Phosphorylated Proteins in Stationary Growth Phase

In this paper, we present a comprehensive analysis of protein phosphorylation in the Gram-positive enteropathogen Clostridioides difficile . To date, only limited evidence on the role of phosphorylation in the regulation of this organism has been published; the current study is expected to form the basis for research on this posttranslational modification in C. difficile .

LuxS modulates motility and secretion of extracellular protease in fish pathogen Vibrio harveyi

In this study, an in-frame deletion of the luxS gene was constructed to reveal the role of LuxS in the physiology and virulence of V. harveyi. The statistical analysis showed no significant differences in the growth ability, biofilm formation, antibiotic susceptibility, virulence by intraperitoneal injection, and the ability of V. harveyi to colonize the spleen and liver of the pearl gentian grouper between the wild-type (WT) and the luxS mutant. However, the deletion of luxS decreased the secretion of extracellular protease, while increased the ability of swimming and swarming. Simultaneously, a luxS-deleted mutant showed overproduction of lateral flagella, and an intact luxS complemented the defect. Since motility is flagella dependent, 16 of V. harveyi flagella biogenesis related genes were selected for further analysis. Based on quantitative real-time reverse transcription-PCR (qRT-PCR), the expression levels of these genes, including the polar flagella genes flaB, flhA, flhF, flhB, flhF, fliS, and flrA and the lateral flagella genes flgA, flgB, fliE, fliF, lafA, lafK, and motY, were significantly up-regulated in the ΔluxS: pMMB207 (ΔluxS+) strain as compared with the V. harveyi 345: pMMB207 (WT+) and C-ΔluxS strains during the early, mid-exponential, and stationary growth phase.

Three Stages of Composite Specimen Destruction in Static Failure

The paper presents the results of standard specimen fracture made of anisotropic carbon fiber plastic with an epoxy matrix. Static stepwise loading of the specimen was carried out on an Instron 8801 testing machine to determine the characteristics of ductile fracture G1C in the first mode in accordance with ASTM D5528. During loading, the parameters of acoustic emission (AE) signals, such as AE impulse amplitudes and their energy were synchronously recorded. At the same time, the magnitude of the opening and the growth of the crack initiated by the artificial cut at the end of the specimen were recorded. According to the analysis of the acoustic emission signals, three zones with different G1C behaviour were identified: initial crack propagation, its stationary growth and accelerated fracture of the specimen. The zonal character of the change in the acoustic emission signals made it possible to determine the energy of the acoustic emission signals as diagnostic evidence for the onset of rapid destruction of the specimen. The amplitude of the AE-signals in the zones, however, remained constant. Online monitoring of changes in the energy of acoustic emission signals will prevent the onset of rapid destruction of an object in places of its deformations. The paper does not aim at defining G1C as usual. It presents the investigation of the fracture stages for a composite material using an acoustic emission method.

Two Novel Semisynthetic Lipoglycopeptides Active against Staphylococcus aureus Biofilms and Cells in Late Stationary Growth Phase

The increase in antibiotic resistance among Gram-positive bacteria underscores the urgent need to develop new antibiotics. New antibiotics should target actively growing susceptible bacteria that are resistant to clinically accepted antibiotics including bacteria that are not growing or are protected in a biofilm environment. In this paper, we compare the in vitro activities of two new semisynthetic glycopeptide antibiotics, MA79 and ERJ390, with two clinically used glycopeptide antibiotics—vancomycin and teicoplanin. The new antibiotics effectively killed not only exponentially growing cells of Staphylococcus aureus, but also cells in the stationary growth phase and biofilm.

A general model of the dynamics of genes with dual σ factor preference

Escherichia coli uses the ability of σ factors to recognize specific DNA sequences in order to quickly control large gene cohorts. While most genes respond to only one s factor, approximately 5% have dual s factor preference. The ones in significant numbers are ‘σ 70+38 genes’, responsive to σ 70 , which controls housekeeping genes, as well as to σ 38 , which activates genes during stationary growth and stresses. We show that σ 70+38 genes are almost as upregulated in stationary growth as genes responsive to σ 38 alone. Also, their response strengths to σ 38 are predictable from their promoter sequences. Next, we propose a sequence- and σ 38 level-dependent, analytical model of σ 70+38 genes applicable in the exponential, stationary, and in the transition period between the two growth phases. Finally, we propose a general model, applicable to other σ factors as well. This model can guide the design of synthetic circuits with sequence-dependent sensitivity and plasticity to transitions between the exponential and stationary growth phases.

Lipid and Fatty Acids Accumulation Features of Entomoneis cf. paludosa during Exponential and Stationary Growth Phases in Laboratory Culture

Diatoms are capable of accumulating substantial amounts of triacylglycerides in their cells, which differ in the composition of fatty acids depending on the conditions of cultivation, making them attractive subjects in biotechnology. In the present study, we characterized the structural features of lipid bodies in the diatom Entomoneis cf. paludosa (W. Smith) Reimer strain 8.0727-B and revealed the peculiarities of fatty acid composition in cultures during the stationary and exponential growth phases. Laser scanning confocal microscopy revealed an increased number of lipid bodies in the cytoplasm during the stationary phase of culture growth. Electron microscopy of ultrathin sections showed that an extreme increase in the number and size of plastoglobules in the cells occurs in the stationary phase of culture growth. The gas chromatography with mass spectrometric detection method revealed differences in the fatty acid composition depending on the growth phase. The studied strain can be recommended as a source of hexadecanoic and octadecanoic fatty acids from the culture during the stationary growth phase, as well as eicosapentaenoic fatty acid from the culture during the exponential growth phase.

Evidence of starch accumulation in TBY-2 cells in the presence of auxin

Tobacco cell suspension (TBY-2) is known to produce starch when cultured in medium supplemented with cytokinin or in hormone-free medium. Unexpectedly, TBY-2 cells, continuously cultivated on auxin alone, were also able to accumulate starch at the beginning of stationary growth phase with a yield of 9.22 ± 0.68 percent. This starch production was strongly correlated with a 25-fold increase in starch synthase activity. Moreover, this TBY-2 line was able to produce an amylopectin-rich starch with a ratio amylopectin over amylose of 2.7 which also linked to typical small granules (size around 1.4 µm). According to our preliminary results, this plant cell suspension could produce a low-cost amylopectin rich starch needed in the food industry for production of edible film or bioplastic without impacts from climate or season changes.

Freeing Aspergillus fumigatus of Polymycovirus Infection Renders It more Resistant to Competition with Pseudomonas aeruginosa due to Altered Iron-Acquiring Tactics

A virus-free (VF) A. fumigatus isolate has been shown to be resistant in competition with Pseudomonas as compared to the isogenic line infected with Aspergillus fumigatus polymycovirus 1 (AfuPmV-1), and this phenotype was apparently related to alterations in iron metabolism. Here we investigated further the mechanisms underpinning this phenotype. The extracellular siderophore profiles of five isogenic VF and virus-infected (VI) strains were sampled at 24, 31, 48, 54, and 72 h in submerged cultures and quantitatively examined by liquid chromatography and mass spectrometry. Intracellular profiles of conidia and cultures at the stationary growth phase were defined. VF A. fumigatus demonstrated the best fitness represented by the fastest onset of its exponential growth when grown on an iron-limited mineral medium. The exponential phase and transitional production phase of the extracellular triacetylfusarinine C (TafC) were achieved at 24 and 31 h, respectively, contrary to VI strains, which acted more slowly. As a result, the TafC reservoir was consumed sooner in the VF strain. Additionally, the VF strain had lower ferricrocin and higher hydroxyferricrocin content in the pellet during the stationary phase. All of these differences were significant (Kruskal–Wallis, p < 0.01). In our study, the siderophore reservoir of a VF strain was consumed sooner, improving the fitness of the VF strain in competition with P. aeruginosa.