Bacteria, Volume 3, Issue 4 (December 2024) – 16 articles

Pseudomonas cannabina pv. alisalensis (Pcal) causes bacterial blight on cabbage. In a previous study, we screened for reduced virulence using Tn5 transposon mutants and identified a LysR-type transcriptional regulator (LTTR) as a potential virulence factor in Pcal. However, the role of LTTR in Pcal virulence has not been thoroughly investigated. In this study, we demonstrated that the Pcal NN14 mutant (with Tn5 insertion in the LTTR-encoding gene) showed reduced disease symptoms and bacterial populations in cabbage, indicating that LTTR contributes to Pcal virulence. RNA-seq analysis identified 39 LTTR-dependent genes. Genes associated with 13 of the type three secretion system (T3SS), two of flagellar apparatus, ABC transporters, and transcription factors were expressed at lower levels in the NN14 mutant compared to the wild type. Conversely, tssH and hcp, type six secretion system (T6SS)-related genes, showed higher expression in NN14. Furthermore, these differences in gene expression were observed in minimal medium, but not in nutrient-rich medium, suggesting that LTTR acts as a global regulator responsive to nutrient conditions. Additionally, LTTR activated the expression of T3SS-related genes during Pcal infection. We also demonstrated that NN14 showed a reduced ability to induce hypersensitive reaction (HR) cell death in non-host plants. Collectively, these results suggest that LTTR contributes to Pcal virulence by regulating T3SS in response to environmental changes. Full article

The style is the female reproductive channel in flowers, receiving pollen and transmitting male gametes through elongating pollen tubes to the ovules during fertilization. In maize/corn, the styles are known as silks. Fertilization-stage silks contain diverse bacteria, possibly originating from pollen. Bacteria were cultured and individually sequenced from the tip and base portions of healthy, fertilization-stage silks of 14 North American maize genotypes, resulting in 350 isolates, spanning 48 genera and 221 OTUs. The objective of this study was to taxonomically analyze these bacteria in the context of the maize host tissue and genotype, taking advantage of long-read (V1–V9) 16S Sanger sequencing. The results suggest that the maize genotype and heterotic breeding group may impact the bacterial diversity of healthy, fertilization-stage silks. Some taxa were relatively conserved across maize genotypes and silk tip/base locations, including Pantoea, which may represent part of the core microbiome or form stable, symbiotic relationships with healthy, pollinated silks. We also observed similarities between the silk microbiomes of maize genotypes that were related by plant pedigree; these preliminary results suggest inheritance or the ability of related genotypes to recruit common bacterial taxa. Overall, this study demonstrates that healthy maize silks represent a valuable resource for learning about relationships between plant reproductive microbiomes. Full article

Antibiotic-resistance (ABR) poses a critical public health challenge within the broader antimicrobial resistance crisis. This review evaluates the potential of polyelectrolytes (PEs) and polyelectrolyte complexes (PECs) for controlled antibiotic delivery as a strategy to combat ABR and biofilm-related infections. PECs, particularly those incorporating chitosan and other polycations, enhance antibacterial efficacy by disrupting bacterial cell walls and obstructing their nutrient flow. They are also effective in penetrating biofilms and providing sustained drug release. Despite these advantages, there is a need for further in vivo research and clinical trials to validate these findings. This review provides a comprehensive overview of PECs’ potential to advance antibacterial therapies and outlines future research directions to further explore their applications. Full article

Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that play a crucial role in sustainable agriculture by enhancing plant growth through various mechanisms. This review examines the contributions of PGPR in improving nutrient availability, producing phytohormones, providing biocontrol against pathogens, and enhancing abiotic stress tolerance. By reducing the necessity for chemical fertilizers and pesticides, PGPR mitigate environmental impacts, enhance soil health, and support long-term agricultural productivity. However, challenges such as inconsistent performance across various soils, regulatory barriers, and limited farmer awareness, hinder their widespread adoption. Recent advancements in nano-encapsulation technology, genetic engineering, and bioinformatics, present promising solutions for overcoming these obstacles and enhancing PGPR efficacy. The incorporation of PGPR into biofertilizers, biopesticides, and integrated plant management (IPM) offers a sustainable resolution to global agricultural challenges. This review addresses the current state of PGPR research, applications, and future directions for optimizing their use in promoting sustainable agriculture. Full article

Health care providers are an integral part of the era of mobile phones. During various activities linked to health care services, they come in contact with their cell phones regularly. These cell phones act as a perfect substrate for nosocomial pathogens, especially in hot–humid conditions, and may serve as a vehicle in transmitting nosocomial infections. This study aimed at determining the profile of bacteria isolated from the cell phones of healthcare providers. A descriptive cross-sectional study was carried out from 1 April to 3 June 2023, where 115 swab samples were collected from the cell phones of health care providers (laboratory personnel, nurses/midwives and doctors) at the Regional Hospital Bamenda. These swabs were inoculated on blood, chocolate and Mac Conkey plates, and the bacteria were identified according to standard microbiological methods and biochemical tests to the genus/specie level. Data were statistically analyzed using the Statistical Package for Social Sciences (SPSS) version 23. The results were presented in frequencies and proportions. The chi square test was used to compare proportions between variables, and the results were considered statistically significant when p < 0.05. The bacteria isolated from these cell phones included coagulase-negative Staphylococci (CoNS), Staphylococcus aureus, Streptococcus species, Pseudomonas aeroginosa, Escherichia coli, Bacillus species and Neisseria species. All the cell phones of the laboratory personnel were contaminated, followed by those of the nurses/midwives (38; 33.0%) and, lastly, by those of the medical doctors (24; 20.9%). No statistically significant difference was observed between the three categories of health care providers with respect to the presence or absence of bacteria on their cell phones. This study presented that the mobile phones of health care providers are a risk of nosocomial pathogens. The result implies that there is an urgent need to implement and emphasize strategies such as hand washing and decontamination of mobile phones to limit nosocomial infections in the hospital. Full article

Background: Bacterial infections constitute a large portion of infectious disorders. The location of culture-positive specimens and profiles of antibiotic resistance for common pathogens have been the focal points of subsequent investigations. Methodology: The diagnosis of microbiology was carried out using traditional culture techniques. In accordance with Clinical and Laboratory Standards Institute guidelines, the Kirby–Bauer disk diffusion method was employed for antimicrobial susceptibility analysis. The data were extracted from WHONET 2022 software version 22.5.5 and analyzed using SPSS software. Results: In total, 2489 pathogens were isolated from 2073 patients in three consecutive years. About 768 (34.9%) of the isolates were from the neonatal intensive care unit and the pediatric wards, and 63.2% isolates were from blood specimens. The ESKAPE pathogens were predominant (67%). About 100 Enterobacteriaceae family member bacteria were resistant to carbapenem drugs, and 320 isolates of this family were expected to be beta lactamase producers. A total of 120 methicillin-resistant S. aureus isolates were also identified. Conclusions: Among the isolates, ESKAPE pathogens accounted for the greatest proportion. Most isolates were from the neonatal intensive care unit. A significant number of multidrug-resistant, extreme drug-resistant, and pandrug-resistant isolates were identified in the present study. Full article

Fungal infections significantly threaten public health, and many strains are resistant to antifungal drugs. Marine Actinobacteria have been identified as the generators of powerful bioactive compounds with antifungal activity and can be used to address this issue. In this context, strains of Actinomycetes were isolated from the marine area of Rachgoun Island, located in western Algeria. The isolates were phenotypically and genetically characterized. The most potent antifungal isolate was selected, and its crude extract was purified and characterized by the GC/MS method. The results revealed that the STR2 strain showed the strongest activity against at least one target fungal species tested on a panel of fungal pathogens, including Candida albicans, Aspergillus fumigatus, Aspergillus niger, and Fusarium oxysporum. The molecular assignment of the STR2 strain based on the 16S rRNA gene positioned this isolate as a Streptomyces bacillaris species. The presence of safranal (2,3-dihydro-2,2,6-trimethylbenzaldehyde) in the crude chloroform extract of Streptomyces bacillaris STR2 strain was discovered for the first time in bacteria using chromatographic analysis of its TLC fractions. Moreover, certain molecules of biotechnological interest, such as phenols, 1,3-dioxolane, and phthalate derivatives, were also identified. This study highlights the potential of marine actinomycetes to produce structurally unique natural compounds with antifungal activity. Full article

Plant pathogenic Pseudomonas species cause a variety of diseases in plants. Each Pseudomonas species employs different virulence factors and strategies for successful infection. Moreover, even the same bacterial pathogens can differentially utilize virulence factors against various host plants. However, there has been relatively less emphasis on comparing the infection strategies of a single bacterial pathogen on different hosts and different bacterial pathogens on a single host. Here, we investigated plant–pathogen interactions using two Pseudomonas species, Pseudomonas cannabina pv. alisalensis (Pcal) KB211 and Pseudomonas syringae pv. tomato (Pst) DC3000, and their host plants, cabbage and tomato. Our findings reveal distinct behaviors and virulence patterns across different host plants. Pcal multiplies to greater levels in cabbage compared to tomato, suggesting that Pcal is more adaptive in cabbage than tomato. Conversely, Pst showed robust multiplication in tomato even at lesser inoculum levels, indicating its aggressiveness in the apoplastic space. Gene expression analyses indicate that these pathogens utilize distinct virulence-related gene expression profiles depending on the host plant. These insights highlight the importance of revealing the spatiotemporal regulation mechanisms of virulence factors. Full article

Streptococcus mutans is primarily found in biofilms on tooth surfaces and is associated with the development of dental caries. S. mutans synthesizes water-insoluble glucan (WIG) using sucrose as a substrate, inducing the formation of three-dimensional biofilms. WIG is produced by glucosyltransferases (GTFs) encoded by the tandem and highly homologous gtfB and gtfC genes. Conversely, the homologous recombination of gtfB and gtfC readily happens, producing natural variants without WIG. These WIG⁻ variants are thought to have ecologically pleiotropic functions; however, the molecular basis for their appearance is unclear. This study aimed to determine the sequence of the gtfB–gtfC regions of WIG⁻ variants. We sequenced the gtfB–gtfC regions of 23 WIG⁻ variants derived from S. mutans UA159 and revealed the presence of five alleles and four types of single homologous recombination patterns. Regardless of the allele type, the WIG⁻ variants showed low biofilm formation and GTF activity. To the best of our knowledge, this is the first study to report the presence of alleles in WIG⁻ variants. These findings provide important information for explaining the appearance of mechanisms in WIG⁻ variants. Full article

Platelets are well known for their role in hemostasis. Additionally, platelets play a crucial role in immune and inflammatory responses. Toll-like receptors (TLRs) can mediate bacterial interactions during infection, triggering platelets to initiate an inflammatory response. TLR-4 receptors enable direct interactions between platelets and the bacterial lipopolysaccharide (LPS) endotoxin. The aim of this study was to assess platelet plug formation in response to LPS from Proteus mirabilis. Human whole blood was treated with varying concentrations of LPS over a range of incubation times. Then, platelet plug formation time was measured, under high shear conditions using the platelet function analyzer PFA-100, as aperture closure time (CT). The addition of either 2 or 10 µg/mL of LPS to 80% whole blood significantly prolonged the CTs even in the absence of preincubation (p = 0.028 or p = 0.049, respectively). With added preincubation of LPS with whole blood, the measured CTs were further prolonged. If the preincubation time was set to 35 min, then even the addition of 0.2 µg/mL of LPS resulted in significant CT prolongation (p < 0.001). Taken together, the platelet plug formation in the presence of collagen/ADP is significantly prolonged by the presence of LPS in a concentration and preincubation time-dependent manner. Exposure to P. mirabilis LPS reduces the platelet aggregation response in human whole blood. Full article

Ceramic and vitreous materials can be functionalized to exhibit biocidal activity. This research evaluates the biocidal properties of silver-modified vitreous microspheres designed to be included in water endpoints and siphons to prevent nosocomial diseases produced in hospital environments. The microspheres obtained from a coating and heat treatment process at 650 °C have been chemically and microstructurally characterized using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Wavelength Dispersive X-ray Fluorescence (WD-XRF), Scanning Electron Microscopy (FEG-SEM) and Energy-dispersive X-ray Microanalysis (EDS) to determine how silver particles are distributed in the glassy matrix and to relate their bactericidal capacity by means of leaching tests. Microbiological tests have been performed against microorganisms such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida auris. The results revealed that these silver-coated microspheres had significant bactericidal activity, with a significant reduction in the population of E. coli, C. auris, and P. aeruginosa, with no cytotoxic effect of these microspheres. Full article

Antiphospholipid syndrome (APS), also known as Hughes syndrome, is a systemic autoimmune disorder characterized by recurrent thrombosis and pregnancy complications, accompanied by the presence of antiphospholipid antibodies (aPLs). These antibodies target anionic phospholipids or protein–phospholipid complexes within cell membranes, contributing to the underlying mechanisms of the disease. Although anticoagulation therapy remains the cornerstone of APS management, it often fails to prevent complications, particularly in obstetric and thrombotic cases. As autoimmune diseases become increasingly linked to alterations in the gut microbiome, this study investigates the complex interaction between gut bacteria and immune modulation in APS. We explore how disruptions in the gut microbiome may influence the development of autoimmune conditions, with a specific focus on APS. By identifying key microorganisms potentially involved in this gut–immune axis, we aim to provide insights into novel preventive and control approaches. Future research should focus on harnessing the gut microbiome to develop more effective treatments that target both the immune system and microbial populations in APS patients. Full article

Bioremediation, the degradation of environmental pollutants by living organisms, has immense potential to lead to a greener planet. Bioinformatics analysis can contribute to the identification of novel microorganisms, which biodegrade contaminants, or of participating proteins and enzymes, and the elucidation of the complex metabolic pathways involved. In this study, we focus on C-P lyase and glyphosate oxidoreductase (Gox), two enzymes which degrade glyphosate, a widely used pesticide. Amino acid sequences of the two enzymes were collected from a broad range of microorganisms using the KEGG database and BLAST. Based on this, we identified additional lineages, with putative glyphosate-degrading activity, for which no glyphosate-degrading species have been reported yet. The conserved residues in each enzyme were identified via multiple alignments and mapped onto the 3D structures of the enzymes, using PyMOL, leading to novel insights into their function. As the experimental structure of Gox is still unknown, we created structural models based on three different programs and compared the results. This approach can be used to yield insights into the characteristics of potential glyphosate-degrading enzymes. Given the limited information available, such a step is important to gain further knowledge about them, which can contribute to their application in bioremediation in the future. Full article

In recent years, the study of antimicrobial peptides (AMPs) has garnered considerable attention due to their potential in combating antibiotic-resistant pathogens. Mass spectrometry-based proteomics provides valuable information on microbial stress responses induced by AMPs. This work aims to unravel the proteomic alterations induced by the amyloidogenic antimicrobial peptide R23I, encompassing both inhibitory and non-inhibitory concentrations. This study investigates the effects of the R23I peptide on the protein abundance of Thermus thermophilus (T. thermophilus) at different concentrations (20, 50, and 100 μg/mL). We found 82 differentially expressed proteins, including 15 upregulated and 67 downregulated proteins. We also compared the protein identification results between the PEAKS and IdentiPy programs. Our proteomic analysis revealed distinct patterns of protein expression, suggesting compensatory mechanisms in response to the R23I peptide. Notably, the alterations predominantly affected membrane and cytoplasmic proteins that play a central role in critical cellular processes such as transcription, translation, and energy conversion. This study sheds light on the complex interactions between antimicrobial peptides and bacterial responses, offering insights into microbial adaptability and potential implications for antimicrobial strategies and the understanding of microbial physiology. Full article

Maize silks (style) receive wind-transmitted pollen. Thereafter, male gametes travel through the silks to reach ovules. Pollinated silks contain a microbiome, members of which are predicted to promote host reproduction and abiotic/biotic stress tolerance during fertilization. It is unknown whether pollinated silk bacteria originate environmentally (air/pollen) or from maternal tissue. Methods are lacking to test microbial colonization of silks in their native habitat [on intact maize inflorescences (cobs) encased by husk leaves]. Current methods focus on naked silks attached to dehusked cob pieces. Here, two novel methods are presented to enable research on silk microbes in their native habitat. Method 1 tests whether silk-associated bacteria with potential environmental origins are attracted toward ovules. Method 2 distinguishes whether a microbe colonizes silks from the environment or maternal parent. Biosafety containment was enabled by housing microbe-treated cobs in large jars. Using these methods, a model bacterial isolate from fertilization-stage silks (DsRed-tagged Pantoea-E04) was shown to colonize husk-covered silks after inoculating exposed silk tips; E04 could not colonize from the cob base, suggesting an environmental origin. In support, E04 colonized silks more frequently when cobs were uncut and oriented vertically. These protocols will enable more biologically relevant investigation of silk microbiomes and pathogens. Full article

The need for sustainable farming practices has brought attention to biofertilizers to improve soil quality and boost crop yield while minimizing environmental impacts. This study explores the potential integration of biofertilizers within push–pull cropping systems, an agroecological approach that utilizes companion cropping to repel and attract pests. This review focuses on how biofertilizers could optimize plant–microbe interactions, promoting nutrient uptake, pest control, and soil health. Key biofertilizers, including nitrogen-fixing, phosphate-solubilizing, and potassium-solubilizing bacteria, improve nutrient availability, which leads to higher crop yields and resilience. They also enhance soil water retention and drought tolerance, which are crucial under changing climate conditions. Biofertilizers support beneficial microbial communities, reducing reliance on synthetic fertilizers and pesticides while fostering disease suppression and stress tolerance in crops. Their effectiveness can be significantly increased when biofertilizers are integrated with push–pull technology (PPT). However, challenges remain, such as inconsistent biofertilizer performance and the complexity of microbial interactions. Overcoming these challenges necessitates a multidisciplinary approach to refining production and application techniques. This study emphasizes the need to investigate biofertilizer-mediated plant–microbiome dynamics further to unlock their full potential. It concludes that future research should focus on the synergies between biofertilizers and agroecological systems to enhance food security and environmental sustainability. This work advances our understanding of optimizing biofertilizers in sustainable farming practices, particularly within the PPT framework. Full article