Screening and Molecular Identification of Bacteria from the Midgut of Amphimallon solstitiale Larvae Exhibiting Antagonistic Activity against Bacterial Symbionts of Entomopathogenic Nematodes

Entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) are a group of organisms capable of infecting larvae of insects living in soil, including representatives of the family Scarabaeidae. Their insecticidal activity is related to the presence of symbiotic bacteria Xenorhabdus spp. or Photorhabdus spp. in the alimentary tract, which are released into the insect body, leading to its death caused by bacterial toxins and septicemia. Although the antibacterial activities of symbionts of entomopathogenic nematodes have been well described, there is insufficient knowledge of the interactions between these bacteria and microorganisms that naturally inhabit the alimentary tract of insects infested by nematodes. In this study, 900 bacterial strains isolated from midgut samples of Amphimallon solstitiale larvae were tested for their antagonistic activity against the selected five Xenorhabdus and Photorhabdus species. Cross-streak tests showed significant antibacterial activity of 20 isolates. These bacteria were identified as Bacillus [Brevibacterium] frigoritolerans, Bacillus toyonensis, Bacillus wiedmannii, Chryseobacterium lathyri, Chryseobacterium sp., Citrobacter murliniae, Enterococcus malodoratus, Paenibacillus sp., Serratia marcescens and Serratia sp. Since some representatives of the intestinal microbiota of A. solstitiale are able to inhibit the growth of Xenorhabdus and Photorhrhabdus bacteria in vitro, it can be assumed that this type of bacterial interaction may occur at certain stages of insect infection by Steinernema or Heterorhabditis nematodes.

Effect of a mannose to the interactions between Naegleria fowleri and pathogenic bacteria

Introduction and Aim: In this study, the interaction between pathogenic Naegleria fowleri and pathogenic bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis and Salmonella typhi was analyzed by a monosaccharide of mannose. Moreover, since the form of N. fowleri was found in diseases as cysts, the interaction between cysts and bacteria was analyzed. Materials and Methods: In order to analyze the role of a monosaccharide called mannose in bacterial interaction, the analysis of bacterial association, invasion, and survival for amoeba treated with mannose was performed. N. fowleri trophozoites or cysts were pre-treated with a mannose at a concentration of 10, 50 and 100 mM for 1 hr at 37°C. Results: The MRSA association was hardly suppressed until the concentration of mannose was 50 mM, but its association was reduced by about 168% to N. fowleri trophozoites by 100 mM mannose. Compared to the results for MRSA, the association of E. faecalis had little effect by mannose. Very interestingly, although S. typhi showed much higher invasion than the above MRSA and E. faecalis, it did not survive at all within N. fowleri trophozoites. Ten mM mannose showed a nearly similar 1% association with N. fowleri cyst treated, but not with 50 mM and 100 mM mannose treated N. fowleri cyst at all. Conclusion: The association and invasion of S. typhi was highest for N. fowleri trophozoites and cysts, but the three bacteria did not survive in N. fowleri trophozoites and cysts.

Phenotypic plasticity and a new small molecule are involved in a fungal-bacterial interaction

Nitrogen-fixing bacteria have been extensively studied in the context of interactions with their host plants; however, little is known about the phenotypic plasticity of these microorganisms in nonmutualistic interactions with other eukaryotes. A dual-species coculture model was developed by using the plant symbiotic bacterium Rhizobium etli and the well-studied eukaryote Saccharomyces cerevisiae as a tractable system to explore the molecular mechanisms used by R. etli in nonmutual interactions. Here, we show that the fungus promotes the growth of the bacterium and that together, these organisms form a mixed biofilm whose biomass is ~ 3 times greater and is more structured than that of either single-species biofilm. We found that these biofilm traits are dependent on a symbiotic plasmid encoding elements involved in the phenotypic plasticity of the bacterium, mitochondrial function and in the production of a yeast-secreted sophoroside. Interestingly, the promoters of 3 genes that are key in plant bacteria-interaction (nifH, fixA and nodA) were induced when R. etli coexists with yeast. These results show that investigating interactions between species that do not naturally coexist is a new approach to discover gene functions and specialized metabolites in model organisms.

Multidrug-Resistance and Virulence-Related Properties of Diarrheagenic Escherichia Coli in Urban River: A Possible Source and Dissemination of Human Infections

The presence of multi-drug resistant (MDR) E. coli harboring virulence pathotypes in aquatic systems is a public health concern due to an increase number of cases of infections and outbreaks in industrialized and developing countries. The aim of the present study was to evaluate the microbiological quality of Joana river, located at Rio de Janeiro, by analyzing E. coli bacteria contamination and to investigate virulence properties and MDR profiles by phenotypic and genotypic methods, including bacterial interaction with Caco-2 cells. A total of 34 E. coli were identified by MALDI-TOF and 20 E. coli were characterized as MDR when submitted to antimicrobial susceptibility test. Evaluation by multiplex-PCR of MDR E. coli demonstrated the presence of virulence pathotypes: EHEC (stx1, stx2, eae genes), STEC (stx2 gene) and EIEC/STEC (stx2, iaL genes). Virulence potential was demonstrated by the ability to adhere and survive within Caco-2 cells of MDR E. coli pathotypes (n = 4). In conclusion, this study demonstrates the presence of diarrheagenic MDR E. coli in river water at Rio de Janeiro. The possibility of aquatic environment dissemination of antimicrobial resistance and human contamination leading to community and nosocomial infections due to virulent MDR E. coli water-borne pathogens is a matter of concern.

New Insight into Bacterial Interaction with the Matrix of Plant-Based Fermented Foods

Microorganisms have been harnessed to process raw plants into fermented foods. The adaptation to a variety of plant environments has resulted in a nearly inseparable association between the bacterial species and the plant with a characteristic chemical profile. Lactic acid bacteria, which are known for their ability to adapt to nutrient-rich niches, have altered their genomes to dominate specific habitats through gene loss or gain. Molecular biology approaches provide a deep insight into the evolutionary process in many bacteria and their adaptation to colonize the plant matrix. Knowledge of the adaptive characteristics of microorganisms facilitates an efficient use thereof in fermentation to achieve desired final product properties. With their ability to acidify the environment and degrade plant compounds enzymatically, bacteria can modify the textural and organoleptic properties of the product and increase the bioavailability of plant matrix components. This article describes selected microorganisms and their competitive survival and adaptation in fermented fruit and vegetable environments. Beneficial changes in the plant matrix caused by microbial activity and their beneficial potential for human health are discussed as well.

Microbial Fuel Cell: Recent Developments in Organic Substrate Use and Bacterial Electrode Interaction

A new bioelectrochemical approach based on metabolic activities inoculated bacteria, and the microbial fuel cell (MFC) acts as biocatalysts for the natural conversion to energy of organic substrates. Among several factors, the organic substrate is the most critical challenge in MFC, which requires long-term stability. The utilization of unstable organic substrate directly affects the MFC performance, such as low energy generation. Similarly, the interaction and effect of the electrode with organic substrate are well discussed. The electrode-bacterial interaction is also another aspect after organic substrate in order to ensure the MFC performance. The conclusion is based on this literature view; the electrode content is also a significant challenge for MFCs with organic substrates in realistic applications. The current review discusses several commercial aspects of MFCs and their potential prospects. A durable organic substrate with an efficient electron transfer medium (anode electrode) is the modern necessity for this approach.

Genomic Sequence Analysis of Methicillin- and Carbapenem-Resistant Bacteria Isolated from Raw Sewage

The reasons for the increasing prevalence of antibiotic-resistant infections are complex and associated with myriad clinical and environmental processes. Wastewater treatment plants operate as nexuses of bacterial interaction and are known hot spots for genetic exchange between bacteria, including antibiotic resistance genes.

Divergent Temporal Response of Abundant and Rare Bacterial Communities to Transient Escherichia coli O157:H7 Invasion

The release of Escherichia coli (E. coli) O157:H7 has been widely found in various environments, but little is known about the probable influence of the transient E. coli O157:H7 invasion on the native microbial community. Here, we investigated the temporal response of two bacterial biospheres (abundant and rare) of two marsh sediments against E. coli O157:H7 during a 60-day incubation. The diversity of both biospheres showed no evident response to O157:H7 invasion. Temporal factor exhibited greater effects on bacterial variation than O157:H7 invasion. We found that O157:H7 invasion led to an increase in the niche breadth of the bacterial community while decreasing the efficiency of bacterial interaction of the abundant taxa. Moreover, the rare biosphere exhibited enhanced stability against O157:H7 invasion compared with the abundant biosphere, acting as the backbone in resisting external disturbance. Furthermore, each subcommunity assembly showed different randomness levels. The stochastic events were relatively more important in constraining the abundant taxa assembly after invasion. Collectively, E. coli O157:H7 exhibited diverse tangible impact on both biospheres, which unearthed differential responses of abundant and rare biosphere against transient microbial invasion.

Macrophage-produced peroxynitrite induces antibiotic tolerance and supersedes intrinsic mechanisms of persister formation

Staphylococcus aureus is a leading human pathogen that frequently causes chronic and relapsing infections. Antibiotic tolerant persister cells contribute to frequent antibiotic failure in patients. Macrophages represent an important niche during S. aureus bacteremia and recent work has identified a role for oxidative burst in the formation of antibiotic tolerant S. aureus . We find that host-derived peroxynitrite, the reaction product of superoxide and nitric oxide, is the main mediator of antibiotic tolerance in macrophages. Using a collection of S. aureus clinical isolates, we find that, despite significant variation in persister formation in pure culture, all strains were similarly enriched for antibiotic tolerance following internalization by activated macrophages. Our findings suggest that host interaction strongly induces antibiotic tolerance and may negate bacterial mechanisms of persister formation, established in pure culture. These findings emphasize the importance of studying antibiotic tolerance in the context of bacterial interaction with the host suggest that modulation of the host response may represent a viable therapeutic strategy to sensitize S. aureus to antibiotics.

Phenotypic Plasticity and a New Small Molecule are Involved in a Fungal-bacterial Interaction

Nitrogen-fixing bacteria have been extensively studied in the context of interactions with their host plants; however, little is known about the phenotypic plasticity of these microorganisms in nonmutualistic interactions with other eukaryotes. A dual-species coculture model was developed by using the plant symbiotic bacterium Rhizobium etli and the well-studied eukaryote Saccharomyces cerevisiae as a tractable system to explore the molecular mechanisms used by R. etli in nonmutual interactions. Here, we show that the fungus promotes the growth of the bacterium and that together, these organisms form a mixed biofilm whose biomass is ~ 3 times greater and is more structured than that of either single-species biofilm. We found that these biofilm traits are dependent on a symbiotic plasmid encoding elements involved in the phenotypic plasticity of the bacterium and on the production of a small molecule secreted by the fungal cells. These results show that investigating interactions between species that do not naturally coexist (new encounters) is a new approach to discover gene functions and specialized metabolites in model organisms.