Bacterial Growth Rate Research Articles

Intercellular mosaic methylation in fast-growing Mycobacterium tuberculosis clinical isolates

Abstract Orphan DNA adenine methyltransferases (MTases) of Mycobacterium tuberculosis (Mtb) exhibit diversity across clinical isolates, but the forces driving this variation are not entirely clear. Recently, we observed several isolates exhibiting anomalous hypomethylation by Type I MTase Mycobacterial Adenine Methyltransferase C (MamC) despite a wild-type mamC genotype (‘MamC-anomalous’ isolates). Investigating this hypomethylation through multiple analyses revealed three key findings. First, heterogeneity analysis revealed intercellular mosaic methylation (IMM) in MamC-anomalous isolates. While they often exhibit phase-variable heterogeneity, this is the first report of IMM by a prokaryotic Type I MTase. Second, MamC-anomalous isolates exhibited a large, stable difference in chromosome copy number along the replication axis (a proxy for bacterial growth rate), suggesting a distinct growth phase accompanied by MamC hypomethylation. Third, MamC methylation efficiency decreased progressively with distance from origin of replication on both strands, with a marked exaggeration in MamC-anomalous isolates. In contrast, other Mtb MTases (MamA and MamB) exhibited lower methylation levels away from the origin only on the lagging strand, and without exaggeration in MamC-anomalous isolates. We conclude that, among Mtb MTases, MamC is uniquely linked to growth dynamics.

Application of the Electrical Microbial Growth Analyzer Method for Efficiently Quantifying Viable Bacteria in Ready-to-Eat Sea Cucumber Products

Accurate and efficient quantification of viable bacteria in ready-to-eat food products is crucial for food safety and public health. The rapid and accurate assessment of foodborne bacteria in complex food matrices remains a significant challenge. Herein a culture-based approach was established for easily quantifying viable bacteria in ready-to-eat sea cucumber (RSC) products. Samples of the liquid companion within the package were directly transferred into test tubes to determine bacterial growth curves and growth rate curves, utilizing the electrical microbial growth analyzer. Viable bacteria in the samples were then quantified based on the time required to attain the maximum growth rate indicated on the growth rate curve. At a concentration of 5.0 × 103 CFU/mL of viable bacteria in the liquid companion, the recovery rates were 108.85–112.77% for Escherichia coli (E. coli) and 107.01–130.54% for Staphylococcus aureus (S. aureus), with standard deviations of 1.60 and 3.92, respectively. For the solid content in the package, the quantification was performed using the same methodology following an additional homogenization step. At a concentration of 5.0 × 103 CFU/mL of viable bacteria in the sample, the recovery rates were 91.94–102.24% for E. coli and 81.43–104.46% for S. aureus, with standard deviations of 2.34 and 2.38, respectively. In instances where the viable bacterial concentration was 5.0 × 103 CFU/mL in RSC products, the total time required for the quantification did not exceed 10.5 h. This method demonstrated advantages over traditional plate counting and PCR methods regarding simplicity and efficiency, representing a promising alternative for the quantification of viable bacteria in food like RSC products.

Exploring the Nexus Between Emulsifier Characteristics and Salmonella Typhimurium Viability in Oil‐in‐Water Emulsions

ABSTRACTMolecular characteristics of emulsifiers such as their molecular weight (MW) and surface charge, not only affect the stability of the emulsion but also can have an impact on its capacity to either inhibit or promote microbial proliferation. These characteristics can affect the behavior of pathogens such as Salmonella Typhimurium in emulsion systems. The growth and thermal resistance of S. Typhimurium were monitored at different oil content levels (20%, 40%, and 60%) in emulsions stabilized by three whey protein‐based emulsifiers: whey protein isolate (WPI), whey protein hydrolysate (WPH), and a modified WPI with an alteration of charge (WPI+). Our study revealed that emulsifier itself with different MW and surface charge had no effect on bacterial growth and inactivation without oil inclusion (p > 0.05). However, it was found that higher bacterial growth rate at 60% oil content emulsion stabilized with WPI+ (0.65 ± 0.03 log CFU/h) than WPI (0.19 ± 0.04 log CFU/h), which showed the charge of emulsifiers has different effects on microbial dynamics in oil‐in‐water emulsion. Interestingly, WPI+ in emulsions also seemed to convey protection against thermal inactivation of bacteria. These data describe a complex interrelationship between the physicochemical characteristics of the emulsifier and its interacting nature with bacterial cells. They throw even more light on the insight about the importance of a strategic approach toward emulsifier selection in food formulations. This is crucial for the food safety and stability of products.

Effects of Thyme (Thymus vulgaris) Essential Oil on Bacterial Growth and Expression of Some Virulence Genes in Salmonella enterica Serovar Enteritidis.

The investigation on natural antimicrobial compounds against zoonotic pathogens has gained more attention due to the public health concerns regarding the emergence of antimicrobial resistance. The current study aimed to assess the effects of thyme essential oil at sub-minimal inhibitory concentrations (sub-MICs) on bacterial growth and expression of some virulence genes in Salmonella enteritidis. The bacterial growth rate and the expression of four virulence genes in S. enteritidis during 18-72h of exposure to the essential oil at 25%-75% MIC were evaluated via colony counting and real-time polymerase chain reaction (PCR), respectively. Sub-inhibitory concentrations of thyme essential oil significantly reduced the growth rate compared to the control. Expression of all tested virulence genes was also reduced by the essential oil in a significant dose- and time-dependent manner. As an example, decreased down-regulation of hilA, spv, sefA and invA as 1.7-, 4.14-, 2.92- and 1.04-fold in 25% MIC and 6.42-, 7.81-, 4.4- and 3.75-fold in 75% MIC was observed, respectively, after 24h of incubation. Likewise, levels of transcription for hilA, spv, sefA and invA were reduced 4.75-, 6.95-, 3.75- and 2.98-fold after 18h and 9.54-, 8.81-, 5.65- and 4.77-fold, respectively, after 72h in 75% MIC compared to the control. According to our data, aside from the growth inhibitory effect of thyme essential oil, the results of current study highlight the potential of thyme for reducing the transcriptional level of virulence genes and therefore the pathogenicity of S. enteritidis.

Evaluation of the Robustness Under Alkanol Stress and Adaptability of Members of the New Genus Halopseudomonas

Many species of the genus Pseudomonas are known to be highly tolerant to solvents and other environmental stressors. Based on phylogenomic and comparative genomic analyses, several Pseudomonas species were recently transferred to a new genus named Halopseudomonas. Because of their unique enzymatic machinery, these strains are being discussed as novel biocatalysts in biotechnology. In order to test their growth parameters and stress tolerance, five Halopseudomonas strains were assessed regarding their tolerance toward different n-alkanols (1-butanol, 1-hexanol, 1-octanol, 1-decanol), as well as to salt stress and elevated temperatures. The toxicity of the solvents was investigated by their effects on bacterial growth rates and presented as EC50 concentrations. Hereby, all Halopseudomonas strains showed EC50 values up to two-fold lower than those previously detected for Pseudomonas putida. In addition, the activity of the cis-trans isomerase of unsaturated fatty acids (Cti), which is an urgent stress response mechanism known to be present in all Pseudomonas species, was monitored in the five Halopseudomonas strains. Although several of the tested species were known to contain the cti gene, no significant phenotypic activity could be detected in the presence of the assayed stressors. A bioinformatic analysis of eight cti-carrying Halopseudomonas strains examining promotor binding sites, binding motifs and signal peptides showed that most of the cti genes have a lipoprotein signal peptide and promotor regions and binding motifs that do not coincide with those of Pseudomonas. These insights represent putative reasons for the absence of the expected Cti activity in Halopseudomonas, which in turn has always been observed in cti-carrying Pseudomonas. The lack of Cti activity under membrane stress conditions when the cti gene is present has never been documented, and this could represent potential negative implications on the utility of the genus Halopseudomonas for some biotechnological applications.

Rapid growth rate of Enterobacter sp. SM3 determined using several methods

BackgroundBacterial growth rate, commonly reported in terms of doubling time, is frequently determined by one of two techniques: either by measuring optical absorption of a growing culture or by taking samples at different times during their growth phase, diluting them, spreading them on agar plates, incubating them, and counting the colonies that form. Both techniques require measurements of multiple repeats, as well careful assessment of reproducibility and consistency. Existing literature using either technique gives a wide range of growth rate values for even the most extensively studied species of bacteria, such as Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. This work aims to apply several methods to reliably determine the growth rate of a recently identified species of Enterobacteriaceae, called Enterobacter sp. SM3, and to compare that rate with that of a well-known wildtype E. coli strain KP437.ResultsWe extend conventional optical density (OD) measurements to determine the growth rate of Enterobacter sp. SM3. To assess the reliability of this technique, we compare growth rates obtained by fitting the OD data to exponential growth, applying a relative density method, and measuring shifts in OD curves following set factors of dilution. The main source of error in applying the OD technique is due to the reliance on an exponential growth phase with a short span. With proper choice of parameter range, however, we show that these three methods yield consistent results. We also measured the SM3 division rate by counting colony-forming units (CFU) versus time, yielding results consistent with the OD measurements. In lysogeny broth at 37oC, SM3 divides every 21 ± 3 min, notably faster than the RP437 strain of E. coli, which divides every 29 ± 2 min.ConclusionThe main conclusion of this report is that conventional optical density (OD) measurements and the colony-forming units (CFU) method can yield consistent values of bacterial growth rate. However, to ensure the reproducibility and reliability of the measured growth rate of each bacterial strain, different methods ought to be applied in close comparison. The effort of checking for consistency among multiple techniques, as we have done in this study, is necessary to avoid reporting variable values of doubling time for particular species or strains of bacteria, as seen in the literature.

Estimation of Staphylococcus total viable count in different contamination states of central venous catheters in hemodialysis centers based on tunable diode laser wavelength‐modulation spectroscopy

AbstractThe surveillance and assessment of the total viable count (TVC) of Staphylococcus under different levels of catheter contamination are crucial for the prevention and evaluation of catheter‐related infections in hemodialysis (HD). This paper demonstrates the noninvasive and accurate measurement of the TVC of Staphylococcus using wavelength‐modulated tunable diode laser absorption spectroscopy (WMAS). The tunable distributed feedback laser with a central wavelength of 2004 nm was employed and the detection limit of 22.5 ppm for carbon dioxide (CO2) produced by Staphylococcus epidermidis was obtained. The growth of Staphylococcus under different medium concentrations was studied, and the results indicated a strong correlation between the growth rate and final TVC of S. epidermidis with the medium concentration. When the degree of catheter contamination was low, resulting in minimal residual nutrient concentration within the catheter, the bacterial growth rate and TVC were effectively suppressed. Therefore, it is proven that WMAS is a user‐friendly, noninvasive, and high signal‐to‐noise ratio technique for monitoring Staphylococcus, making it an effective tool for assessing Staphylococcus growth in HD catheter surveillance.

Developing Flowcharts for Hazard Analysis in Seafood Retail: Critical Control Point Verification

Background: Implementing Hazard Analysis and Critical Control Point (HACCP) management across the supply chain is promoted globally to ensure the safety of marine food products due to their rapid quality deterioration. However, many seafood retail stores deviate from adopting these practices. Therefore, in this study, we aimed to create a flowchart based on HACCP and validate it in retail stores. Methods: Chub mackerel (Scomber japonicus), scallops (Patinopecten yessoensis), and whiteleg shrimp (Litopenaeus vannamei) specimens were purchased from a supermarket from August to December 2020. The handling information of these products from receipt to sales was obtained to prepare an HACCP plan for retail stores. Groups adhering to and deviating from flowchart conditions were categorized as Critical Control Point (CCP)-compliant and CCP-deviant, respectively. Four samples of each product for each condition were analyzed. Bacterial viability was evaluated using the flat agar culture method. Escherichia coli and Vibrio parahaemolyticus were detected using the Brilliant Green-Lactose-Bile and material point methods, respectively. Product freshness was assessed by determining K-values using High-Performance Liquid Chromatography. Results were compared using Student’s t-test. Results: At elevated storage temperatures, bacterial growth rates were higher in chub mackerel and whiteleg shrimp than those in scallops. E. coli was not detected in any sample, whereas V. parahaemolyticus was detected in scallops and whiteleg shrimp but not in chub mackerel. CCP-deviant refrigerated scallops had increased V. parahaemolyticus counts; however, it did not differ between the frozen scallop and whiteleg shrimp. K-values increased more rapidly in CCP-deviant chub mackerel, whiteleg shrimp, and refrigerated scallops, but not in frozen scallops. Inadequate temperature control during display and sale markedly deteriorated the quality of marine products. Conclusion: Setting CCPs for marine food product display and sale while controlling temperature can preserve product quality. The flowchart created in this study can be broadly used for marine retail stores.

Bacterioplankton of the Western Part of the Kara Sea

Data on the structural and production characteristics of bacterioplankton in the western part of the Kara Sea at the beginning and in the middle of summer are presented. In the region of the St. Anna Trough slope, the average abundance of prokaryotes for the water column was (594–708) × 103 cells/ml (26.4–36.5 mgC/m3) in June and (247–517) × 103 cells/ml (12–28 mgC/m3) at the beginning of August. On the transect along Novaya Zemlya, the average abundance of bacterioplankton in the water column was (186–554) × 103 cells/mL (8.5–30 mgC/m3) within a week after the seasonal ice and (169–443) × 103 cells/mL (8–21 mgC/m3) in the midsummer. Bacterial specific growth rate did not exceed 1.28 day–1; its high values were observed in the upper warm water layer, above the halocline, and also at the near-bottom depths. At the beginning of summer, the production of bacterioplankton tended to decrease in the northeast direction. The distribution of prokaryotes abundance was determined by temperature and water saturation with oxygen, possibly as an indirect indicator of past phytoplankton “bloom”.

Bacterial Culture Results and Antibiograms in Chronic Rhinosinusitis Patients in Mekong Delta, Vietnam

Background The inappropriate use of antibiotics for chronic rhinosinusitis, exceeding established guidelines, is a growing concern in Vietnam. This practice is contributing to the emergence and spread of antibiotic-resistant bacteria. Objective This study aimed to evaluate the results of culture and antibiogram of bacteria on patients in the Mekong Delta, Vietnam, who were treated for chronic rhinosinusitis in 2022-2023. Methods It is a cross-sectional study, including 113 patients who came for treatment with a diagnosis of chronic rhinosinusitis at Can Tho University of Medicine and Pharmacy Hospital, Mekong Delta, Vietnam, from 2022-2023. The bacterial cultures were identified, and their antibiograms were performed in the Microbiology laboratory of Can Tho University of Medicine and Pharmacy. Statistical analysis was performed with SPSS version 20.0. Results The rate of bacterial growth was 97.35%. The cultured bacterial composition had 8 genera, 22 species, and 116 samples, of which 2 bacterial species were cultured, accounting for 5.45%. Antibiogram showed that Streptococcus pneumonia was resistant to cefaclor (83.33%), cefuroxime (100%), trimethoprim+ sulfamethoxazole (100%), and susceptible to chloramphenicol (100%) and vancomycin (100%). Streptococcus haemolyticus was resistant to amoxicillin+clavulanic acid (85.71%) and ampicillin (100%) and susceptible to linezolid (100%) and rifampin (100%). Streptococcus epidermidis was resistant to amoxicillin+clavulanic acid (82.35%), ampicillin (100%), penicillin (100%) and susceptible to linezolid (91.18%) and rifampin (88.24%). Streptococcus aureus was resistant to amoxicillin+clavulanic acid (95%) and ampicillin+sulbactam (90%), and susceptible to linezolid (90%) and synercid (95%). Pseudomonas aeruginosa was resistant to amikacin (100%), meropenem (100%) and tobramycin (90%). Conclusion This study offers some useful information to doctors in the Mekong Delta and across Vietnam. It can be used as a good orientation in choosing the most appropriate antibiotics for treating patients with chronic rhinosinusitis. It is important to be conscious of the current trend of the bacteriological profiles and to regulate the antibiotic treatment regime to improve the effectiveness and reduce antibiotic resistance rate.

A Comparative Analysis of Different Xenorhabdus Strains Reveals a Virulent Factor, Cyclic Pro-Phe, Using a Differential Expression Profile Analysis of Non-Ribosomal Peptide Synthetases.

Entomopathogenic bacteria, classified into the genus Xenorhabdus, exhibit a dual lifestyle as mutualistic symbionts to Steinernema nematodes and as pathogens to a broad range of insects. Bacterial virulence depends on toxin proteins that induce toxemia and various immunosuppressive secondary metabolites that cause septicemia. Particularly, the immunosuppressive properties of Xenorhabdus bacteria determine the variability of their insecticidal activities. This study explored the role of peptide metabolites in virulence and its variation among six bacterial strains across three species: X. nematophila, X. bovienii, and X. hominickii. Initially, their virulence significantly varied against a susceptible lepidopteran host, Maruca vitrata, but showed less variation against a tolerant coleopteran host, Tenebrio molitor, with high median lethal bacterial doses. In M. vitrata, virulence was strongly correlated with bacterial growth rate and inhibitory activity against phospholipase A2. Secondly, the six strains differed in the compositions of their secreted secondary metabolites, analyzed by GC-MS following ethyl acetate extraction. Notably, there was significant variation in the production of di- or tetra-peptides. Highly virulent strains commonly produced the cyclic Pro-Phe (cPF). Thirdly, the expression of non-ribosomal peptide synthetase (NRPS) genes varied greatly among the strains. NRPS genes were minimally expressed in the tolerant T. molitor and highly expressed in the susceptible M. vitrata. In M. vitrata, specific NRPS genes were markedly expressed in the virulent strains. Finally, cPF demonstrated potent immunosuppressive activity against the cellular and humoral responses of M. vitrata. The addition of cPF significantly enhanced the virulence against the tolerant T. molitor. These findings suggest that immunosuppression is necessary for the pathogenicity of Xenorhabdus bacteria, wherein NRPS products play a critical role in suppressing immune-associated factors in target insects.

Microbial resistance and resilience to drought across a European climate gradient

Drought and rainfall events will become more frequent and intense with climate change. At the same time, soil moisture is one of the major factors controlling soil microbial processes such as carbon cycling. When challenged with drought there are two main growth responses microorganisms can use: (1) they can maintain growth rates during drought (i.e., resistance) and (2) they can recover growth rates faster when the drought ends (i.e., resilience). Microbial communities are shaped by multiple other factors in the soil environment, however how those impact drought responses remain unclear. Here we investigate how climate (estimated as aridity index) and soil properties determine microbial growth resistance and resilience to drought across a climate gradient in Europe. To test this, we exposed the different soils to a standardised drought cycle in controlled conditions. We assessed bacterial growth, fungal growth and respiration during soil drying to determine resistance and in high resolution during three days after rewetting to estimate resilience to drought. We found that alpha diversity was the strongest driver of both bacterial drought resistance and resilience, which occurred via changes in soil pH. This shows the importance of diversity for sustaining bacterial functions during drought stress. A secondary driver of bacterial drought resistance and resilience was the aridity index was also an important driver, where bacterial communities from more arid climates had higher resistance and resilience to drought. Fungal communities were both more resistant and resilient compared to bacteria, but this was independent of other measured environmental factors. Bacterial resilience was partly linked with differences in community composition. Our results suggest that if sites are exposed to increased aridity due to climate change or are managed to promote bacterial diversity, they will have higher bacterial growth rates during drought perturbations, which could potentially promote soil carbon storage.

Disruptive effects of sewage intrusion into drinking water: Microbial succession and organic transformation at molecular level

Drinking water distribution systems are increasingly vulnerable to sewage intrusion due to aging water infrastructure and intensifying water stress. While the health risks associated with sewage intrusion have been extensively studied, little is known about the impacts of intruded bacteria and dissolved organic matter (DOM) on microbiology in drinking water. In this dynamic study, we demonstrate that the intrusion of 1 % sewage into tap water resulted in immediate contamination, including an 8-fold increase in biomass (TCC), a 48.9 % increase in bacterial species (ASVs), a 12.5 % increase in organic carbon content (DOC), and a 13.5 % increase in unique DOM molecular formulae. Over time, sewage intrusion altered tap water microbiology by accelerating bacterial growth rates (5-fold faster), selectively promoting ASVs in community succession, and producing 998 more unique DOM formulae. More significantly, statistical analysis revealed that the intrusion of 1 % sewage shifted the driving force of bacterial and DOM composition covariance from a DOM-dependent process in tap water to a bacterial-governed process post-intrusion. Our results clearly demonstrate the disruptive effects of sewage intrusion into tap water, emphasizing the urgent need to consider the long-lasting impacts of sewage intrusion in drinking water distribution systems, in addition to its immediate health risks.

Diametral influence of deoxynivalenol (DON) and deepoxy-deoxynivalenol (DOM-1) on the growth of Campylobacter jejuni with consequences on the bacterial transcriptome

BackgroundDeoxynivalenol (DON) is a type B trichothecene mycotoxin that is commonly found in cereals and grains worldwide. The presence of this fungal secondary-metabolite raises public-health concerns at both the agriculture and food industry level. Recently, we have shown that DON has a negative impact on gut integrity, a feature also noticed for Campylobacter (C.) jejuni. We further demonstrated that DON increased the load of C. jejuni in the gut and inner organs. In contrast, feeding the less toxic DON metabolite deepoxy-deoxynivalenol (DOM-1) to broilers reduced the Campylobacter load in vivo. Consequently, it can be hypothesized that DON and DOM-1 have a direct effect on the growth profile of C. jejuni. The aim of the present study was to further resolve the nature of this interaction in vitro by co-incubation and RNA-sequencing.ResultsThe co-incubation of C. jejuni with DON resulted in significantly higher bacterial growth rates from 30 h of incubation onwards. On the contrary, the co-incubation of C. jejuni with DOM-1 reduced the CFU counts, indicating that this DON metabolite might contribute to reduce the burden of C. jejuni in birds, altogether confirming in vivo data. Furthermore, the transcriptomic profile of C. jejuni following incubation with either DON or DOM-1 differed. Co-incubation of C. jejuni with DON significantly increased the expression of multiple genes which are critical for Campylobacter growth, particularly members of the Flagella gene family, frr (ribosome-recycling factor), PBP2 futA-like (Fe3+ periplasmic binding family) and PotA (ATP-binding subunit). Flagella are responsible for motility, biofilm formation and host colonization, which may explain the high Campylobacter load in the gut of DON-fed broiler chickens. On the contrary, DOM-1 downregulated the Flagella gene family and upregulated ribosomal proteins.ConclusionThe results highlight the adaptive mechanisms involved in the transcriptional response of C. jejuni to DON and its metabolite DOM-1, based on the following effects: (a) ribosomal proteins; (b) flagellar proteins; (c) engagement of different metabolic pathways. The results provide insight into the response of an important intestinal microbial pathogen against DON and lead to a better understanding of the luminal or environmental acclimation mechanisms in chickens.

Investigation of the growth kinetics of Streptococcus mutans bacteria on Zr-C coating surfaces deposited on 316L stainless steel substrates

The conducted research aims to describe the kinetics of Streptococcus mutans bacteria growth on the surface of Zr-C coatings with varying carbon content deposited on 316L medical-grade stainless steel substrates.The coatings were deposited using the MS PVD (Magnetron Sputtering Physical Vapour Deposition) technique at a constant temperature of 400C. Varying carbon contents in the coatings were achieved by changing the flow rate of acetylene during the process. The dynamics of bacteria growth cultivated at 37C were examined on the surface of the coatings for incubation times ranging from 0 to 72 hours. Generalised logistic functions were utilised for the mathematical description of the obtained results.The produced coatings exhibited varying carbon content, determining the structural composition ranging from a mixture of metallic Zr and ZrC through stoichiometric zirconium carbide to nanocrystalline grains of ZrC in an amorphous carbon matrix. The obtained results unequivocally demonstrate that in the case of ZrC coatings, the carbon content influences both the bacterial growth rate during the proliferation phase and the final population of bacteria.In the conducted research on bacterial population dynamics, only a single strain of Streptococcus mutans was considered, and the mathematical description was limited to reaching a pseudo-steady state by the population.The proposed model can successfully be adapted to describe the dynamics of other individual strains of bacteria dwelling on metallic surfaces as well as coatings.The proposed model can serve as a tool for studying, among other things, inflexion points of logistic curves, which are considered as the boundary between the dominance of anabolic and catabolic processes in the bacterial population.

Antimicrobial impact of a propolis/PVA/chitosan composite and its prospective application against methicillin resistance bacterial infection

Seriously damaged skin could be infected by methicillin-resistant bacteria, which delays restoration. Propolis has bioactivity linked with its minor components, such as antimicrobials and antioxidants. Active sites in polyvinyl alcohol (PVA) and chitosan (CS) can enhance the nano-loading of natural extracts with activity amelioration. Korean propolis extract (KPE) loading to a nanocomposite possibly enhances its antimicrobial and anti-inflammatory potency. Composites were formed using two PVA/CS structures (1:1; 2:1), and their skin-application appropriateness was determined by mechanical properties, moisture content, water activity, and color. The composite of PVA/CS (1:1) was more practicable for KPE-loading. Increasing KPE concentrations (50, 100, 150, and 200 ng/mL) alters composite bioactivity measured by Fourier transmission infrared (FT-IR). Antibacterial potency of 200 ng KPE/mL was the most effective concentration, followed by 150 ng KPE/mL, against Staphylococcus aureus (MRSA) and Clostridium perfringens. The composite activity was measured as minimum inhibition (MIC) and minimum bacterial concentrations (MBC). At 200 ng KPE/mL, MIC and MBC against MRSA were 14.93 ± 1.21 and 20.21 ± 1.97 mg composite/mL, respectively. Significant inhibition was also recorded for antibiofilm formation, where MRSA growth was not detected after 4 hours of time intervals to the stainless-steel coupon. Compared to planktonic bacteria, the formed barrier of PVA/CS restrained the biofilm matrix formation and supported KPE antimicrobial. The impact of inhibition against biofilm formation depends on two parallel mechanisms (PVA barrier with hydrogen bonds, besides nano-KPE particle penetration into bacterial cells). The KPE-composite application to rats’ wounds shows significantly reduced MRSA infection. The results demonstrate the capability of KPE composite in reducing infection, healing correctly, and restoring hair. The wound swabbed test emphasizes this capacity, in which bacterial growth rate restriction was evaluated using a plate count assay. The results recommended 150 ng KPE/mL loading into CS/PVA (1:1) as an effective anti-pathogenic treatment, particularly against the MRSA infection of wounds.

Penicillin-binding protein 3 sequence variations reduce susceptibility of Pseudomonas aeruginosa to β-lactams but inhibit cell division.

β-lactam antibiotics, which inhibit penicillin-binding protein 3 (PBP3) that is required for cell division, play a key role in treating P. aeruginosa infections. Some sequence variations in PBP3 have been associated with β-lactam resistance but the effects of variations on antibiotic susceptibility and on cell division have not been quantified. Antibiotic efflux can also reduce susceptibility. To quantify the effects of PBP3 variations on β-lactam susceptibility and cell morphology in P. aeruginosa. Nineteen PBP3 variants were expressed from a plasmid in the reference strain P. aeruginosa PAO1 and genome engineering was used to construct five mutants expressing PBP3 variants from the chromosome. The effects of the variations on β-lactam minimum inhibitory concentration (MIC) and cell morphology were measured. Some PBP3 variations reduced susceptibility to a variety of β-lactam antibiotics including meropenem, ceftazidime, cefepime and ticarcillin with different variations affecting different antibiotics. None of the tested variations reduced susceptibility to imipenem or piperacillin. Antibiotic susceptibility was further reduced when PBP3 variants were expressed in mutant bacteria overexpressing the MexAB-OprM efflux pump, with some variations conferring clinical levels of resistance. Some PBP3 variations, and sub-MIC levels of β-lactams, reduced bacterial growth rates and inhibited cell division, causing elongated cells. PBP3 variations in P. aeruginosa can increase the MIC of multiple β-lactam antibiotics, although not imipenem or piperacillin. PBP3 variations, or the presence of sub-lethal levels of β-lactams, result in elongated cells indicating that variations reduce the activity of PBP3 and may reduce bacterial fitness.

Sigma S Involved in Bacterial Survival of Ralstonia pseudosolanacearum

Ralstonia pseudosolanacearum, a plant pathogenic bacterium that can survive for a long time in soil and water, causes lethal wilt in the Solanaceae family. Sigma S is a part of the RNA polymerase complex, which regulates gene expression during bacterial stress response or stationary phase. In this study, we investigated the role of sigma S in R. pseudosolanacearum under stress conditions using a rpoS-defective mutant strain of R. pseudosolanacearum and its wild-type strain. The phenotypes of rpoS-defective mutant were complemented by introducing the original rpoS gene. There were no differences observed in bacterial growth rate and exopolysaccharide production between the wild-type strain and the rpoS mutant. However, the wild-type strain responded more sensitively to nutrient deficiency compared to the mutant strain. Under the nutrient deficiency, the rpoS mutant maintained a high bacterial viability for a longer period, while the viability of the wild-type strain declined rapidly. Furthermore, a significant difference in pH was observed between the culture supernatant of the wild-type strain and the mutant strain. The pH of the culture supernatant for the wild-type strain decreased rapidly during bacterial growth, leading to medium acidification. The rapid decline in the wild-type strain’s viability may be associated with medium acidification and bacterial sensitivity to acidity during transition to the stationary phase. Interestingly, the rpoS mutant strain cannot utilize acetic acid, D-alanine, D-trehalose, and L-histidine. These results suggest that sigma S of R. pseudosolanacearum regulates the production or utilization of organic acids and controls cell death during stationary phase under nutrient deficiency.

The Synthesis of Y-zeolite-modified CaCO3-ZnO Nanocomposites as an Antibacterial Agent

The ability of inorganic antibacterial agents like metal oxides and nanoscale inorganic materials to inhibit bacterial growth rates has yet to receive much research attention. In this study, CaCO3-ZnO/Y-zeolite nanocomposites were created utilizing coprecipitation and impregnation techniques with Ca(CH3COO)2, Zn(CH3COO)2 2H2O, Y-zeolite precursors. Physical and chemical characteristics of nanocomposites have been investigated using XRD, FTIR, and SEM-EDX characterizations. The agar-well diffusion method tested the substance for antibacterial activity against gram-positive and gram-negative bacteria. Nanocomposites have a crystal size range of 35.46-36.53 nm and a crystallinity of 35-37 %, according to the results of XRD analysis. The carbonate groups are visible in FTIR data at wave numbers 1433, 875, and 712 cm-1. The Zn-O absorption band was verified at wave numbers 600-400 cm-1. The Y-zeolite absorption bands at wave numbers 1012-997 cm-1 and 745-746 cm-1 were confirmed. The particle morphology is cube-shaped with irregular sizes. The EDX result showed that the composition consists of 35.92 % calcium, 1.68 % zinc, 44.81 % oxygen, and 13.79 % carbon as elements. With the addition of 2.5 % Y-zeolite, the antibacterial activity of nanocomposites showed the best results, with an inhibition zone diameter of 7.62 mm against Escherichia coli and 6.56 mm against Staphylococcus aureus bacteria.

Paternal and induced gut microbiota seeding complement mother-to-infant transmission

Microbial colonization of the neonatal gut involves maternal seeding, which is partially disrupted in cesarean-born infants and after intrapartum antibiotic prophylaxis. However, other physically close individuals could complement such seeding. To assess the role of both parents and of induced seeding, we analyzed two longitudinal metagenomic datasets (health and early life microbiota [HELMi]: N= 74 infants, 398 samples, and SECFLOR: N= 7 infants, 35 samples) with cesarean-born infants who received maternal fecal microbiota transplantation (FMT). We found that the father constitutes a stable source of strains for the infant independently of the delivery mode, with the cumulative contribution becoming comparable to that of the mother after 1 year. Maternal FMT increased mother-infant strain sharing in cesarean-born infants, raising the average bacterial empirical growth rate while reducing pathogen colonization. Overall, our results indicate that maternal seeding is partly complemented by that of the father and support the potential of induced seeding to restore potential deviations in this process.