Nutritional Competition Research Articles

A novel PhoPQ-potentiated mechanism of colistin resistance impairs membrane integrity in Pseudomonas aeruginosa.

Polymicrobial communities are often recalcitrant to antibiotic treatment because interactions between different microbes can dramatically alter their responses and susceptibility to antimicrobials. However, the mechanisms of evolving antimicrobial resistance in such polymicrobial environments are poorly understood. We previously reported that Mg 2+ depletion caused by the fungus Candida albicans can enable Pseudomonas aeruginosa to acquire significant resistance to colistin, a last-resort antibiotic targeting bacterial membrane. Here, we dissect the genetic and biochemical basis of this increased colistin resistance. We show that P. aeruginosa cells can acquire colistin resistance using three distinct evolutionary trajectories involving mutations in genes involved in lipid A biosynthesis, lipid A modifications that are dependent on low Mg 2+ , and a putative Mg 2+ transporter, PA4824. These mutations confer colistin resistance by altering acyl chains, hydroxylation, and aminoarabinose modification of lipid A moieties on the bacterial outer membrane. In all cases, enhanced colistin resistance initially depends on the low Mg 2+ -responsive PhoPQ pathway, which potentiates the evolution of resistance mutations and lipid A modifications that do not occur without Mg 2+ depletion. However, the PhoPQ pathway is not required to maintain high colistin resistance in all cases. In most cases, the genetic and biochemical changes associated with these novel forms of colistin resistance also impair bacterial membrane integrity, leading to fitness costs. Our findings provide molecular insights into how nutritional competition drives a novel antibiotic resistance mechanism and its ensuing fitness tradeoffs.

Hurdle Concept and the Role of Lactic Acid Bacteria

The hurdle idea is a food preservation technique that includes building up a number of barriers to prevent microbes from growing and prolong the shelf life of perishable goods. The idea of using lactic acid bacteria (LAB), which are essential for food preservation, is one that is significant. Through a variety of processes, including fermentation, competitive exclusion, metabolite generation, biofilm formation, nutritional competition, and metabolic activity, LAB support the hurdle concept. Lactic acid bacteria (LAB) ferment glucose to produce lactic acid, which results in an acidic environment that prevents infections and spoiling germs from growing.

Hurdle Concept and The Role of Lactic Acid Bacteria

The hurdle idea is a food preservation technique that includes building up a number of barriers to prevent microbes from growing and prolong the shelf life of perishable goods. The idea of using lactic acid bacteria (LAB), which are essential for food preservation, is one that is significant. Through a variety of processes, including fermentation, competitive exclusion, metabolite generation, biofilm formation, nutritional competition, and metabolic activity, LAB support the hurdle concept. Lactic acid bacteria (LAB) ferment glucose to produce lactic acid, which results in an acidic environment that prevents infections and spoiling germs from growing. Additionally, LAB generates antimicrobial substances such as hydrogen peroxide, organic acids, and bacteriocins, which work by competitively excluding harmful germs from growing. Furthermore, metabolites of lactic acid bacteria (LAB) such acetic acid, diacetyl, and carbon dioxide enhance the flavor of fermented foods and serve as organic preservatives. Moreover, LAB have the ability to create biofilms that shield them from antimicrobial agents and environmental stressors, increasing their survival and persistence in food matrices. By means of nutritional competition, LAB outcompetes pathogenic or spoilage bacteria in the consumption of available resources, hence restricting their growth. In addition, LAB produces enzymes and antibacterial substances, among other metabolic activities that further impede the growth of infections.

Investigating bacterial diversity involved in the production of vegetable-based ethnic fermented food of North Bengal and their metabolic pathways with reverse ecology approach

Endemic fermented vegetables play a crucial role in local cuisine and culture, with traditionally fermented raw green vegetables such as gundruk being a popular practice in North Bengal and Sikkim, India. However, there is a gap in the microbial profiling of these vegetables. This study aimed to explore the diversity of dominant bacterial populations in fermented leafy vegetables using both culture-dependent and culture-independent methods. In addition to isolating bacteria using conventional methods, we conducted phenotypic and biochemical characterization, community DNA isolation, and amplicon sequencing. We also introduced a new approach in bioinformatics analysis: reverse ecology, which analyzes complementation and competition among participant microbes. In conventional culture-dependent techniques, LAB genera such as Lactobacillus, Enterococcus, Leuconostoc, and Pediococcus have been identified as predominant consortia, whereas metagenomic analysis revealed that the microbiome of fermented dried leafy vegetables was mainly composed of Firmicutes, Proteobacteria, Actinobacteria, Bacteroides, and Planctomycetes at the phylum level. Within the Lactobacillaceae family, predominant types included Lactobacillus, Lactococcus, Pediococcus, Leuconostoc, Enterococcus, Vagococcus, Weissella, and Carnobacterium. The microbial metabolism revealed key pathways, such as carbon metabolism, glycolysis, gluconeogenesis, and glyoxylate. Aromatic amino acid degradation, fatty acid metabolism, amino sugar metabolism, nucleotide sugar metabolism, and biosynthesis of nucleotide sugar pathways were also active. The competition index among microbes and human metabolic data was low (0.32–0.44), indicating minimal competition for nutrition. Complementation indices between bacteria and humans were high (0.76–0.88), suggesting a beneficial impact of gundruk microbial populations on human health.

Sequence and structure analyses of lytic polysaccharide monooxygenases mined from metagenomic DNA of humus samples around white-rot fungi in Cuc Phuong tropical forest, Vietnam

Background White-rot fungi and bacteria communities are unique ecosystems with different types of symbiotic interactions occurring during wood decomposition, such as cooperation, mutualism, nutritional competition, and antagonism. The role of chitin-active lytic polysaccharide monooxygenases (LPMOs) in these symbiotic interactions is the subject of this study. Method In this study, bioinformatics tools were used to analyze the sequence and structure of putative LPMOs mined by hidden Markov model (HMM) profiles from the bacterial metagenomic DNA database of collected humus samples around white-rot fungi in Cuc Phuong primary forest, Vietnam. Two genes encoding putative LPMOs were expressed in E. coli and purified for enzyme activity assay. Result Thirty-one full-length proteins annotated as putative LPMOs according to HMM profiles were confirmed by amino acid sequence comparison. The comparison results showed that although the amino acid sequences of the proteins were very different, they shared nine conserved amino acids, including two histidine and one phenylalanine that characterize the H1-Hx-Yz motif of the active site of bacterial LPMOs. Structural analysis of these proteins revealed that they are multidomain proteins with different functions. Prediction of the catalytic domain 3-D structure of these putative LPMOs using Alphafold2 showed that their spatial structures were very similar in shape, although their protein sequences were very different. The results of testing the activity of proteins GL0247266 and GL0183513 show that they are chitin-active LPMOs. Prediction of the 3-D structures of these two LPMOs using Alphafold2 showed that GL0247266 had five functional domains, while GL0183513 had four functional domains, two of which that were similar to the GbpA_2 and GbpA_3 domains of protein GbpA of Vibrio cholerae bacteria. The GbpA_2 - GbpA_3 complex was also detected in 11 other proteins. Based on the structural characteristics of functional domains, it is possible to hypothesize the role of chitin-active GbpA-like LPMOs in the relationship between fungal and bacterial communities coexisting on decomposing trees in primary forests.

Ethanolamine metabolism through two genetically distinct loci enables Klebsiella pneumoniae to bypass nutritional competition in the gut.

Successful microbial colonization of the gastrointestinal (GI) tract hinges on an organism's ability to overcome the intense competition for nutrients in the gut between the host and the resident gut microbiome. Enteric pathogens can exploit ethanolamine (EA) in the gut to bypass nutrient competition. However, Klebsiella pneumoniae (K. pneumoniae) is an asymptomatic gut colonizer and, unlike well-studied enteric pathogens, harbors two genetically distinct ethanolamine utilization (eut) loci. Our investigation uncovered unique roles for each eut locus depending on EA utilization as a carbon or nitrogen source. Murine gut colonization studies demonstrated the necessity of both eut loci in the presence of intact gut microbiota for robust GI colonization by K. pneumoniae. Additionally, while some Escherichia coli gut isolates could metabolize EA, other commensals were incapable, suggesting that EA metabolism likely provides K. pneumoniae a selective advantage in gut colonization. Molecular and bioinformatic analyses unveiled the conservation of two eut loci among K. pneumoniae and a subset of the related taxa in the K. pneumoniae species complex, with the NtrC-RpoN regulatory cascade playing a pivotal role in regulation. These findings identify EA metabolism as a critical driver of K. pneumoniae niche establishment in the gut and propose microbial metabolism as a potential therapeutic avenue to combat K. pneumoniae infections.

Genome-Wide Characterization and Functional Validation of the ACS Gene Family in the Chestnut Reveals Its Regulatory Role in Ovule Development.

Ovule abortion significantly contributes to a reduction in chestnut yield. Therefore, an examination of the mechanisms underlying ovule abortion is crucial for increasing chestnut yield. In our previous study, we conducted a comprehensive multiomic analysis of fertile and abortive ovules and found that ACS genes in chestnuts (CmACS) play a crucial role in ovule development. Therefore, to further study the function of ACS genes, a total of seven CmACS members were identified, their gene structures, conserved structural domains, evolutionary trees, chromosomal localization, and promoter cis-acting elements were analyzed, and their subcellular localization was predicted and verified. The spatiotemporal specificity of the expression of the seven CmACS genes was confirmed via qRT-PCR analysis. Notably, CmACS7 was exclusively expressed in the floral organs, and its expression peaked during fertilization and decreased after fertilization. The ACC levels remained consistently greater in fertile ovules than in abortive ovules. The ACSase activity of CmACS7 was identified using the genetic transformation of chestnut healing tissue. Micro Solanum lycopersicum plants overexpressing CmACS7 had a significantly greater rate of seed failure than did wild-type plants. Our results suggest that ovule fertilization activates CmACS7 and increases ACC levels, whereas an overexpression of CmACS7 leads to an increase in ACC content in the ovule prior to fertilization, which can lead to abortion. In conclusion, the present study demonstrated that chestnut ovule abortion is caused by poor fertilization and not by nutritional competition. Optimization of the pollination and fertilization of female flowers is essential for increasing chestnut yield and reducing ovule abortion.

Synergistic Brilliance: Engineered Bacteria and Nanomedicine Unite in Cancer Therapy.

Engineered bacteria are widely used in cancer treatment because live facultative/obligate anaerobes can selectively proliferate at tumor sites and reach hypoxic regions, thereby causing nutritional competition, enhancing immune responses, and producing anticancer microbial agents in situ to suppress tumor growth. Despite the unique advantages of bacteria-based cancer biotherapy, the insufficient treatment efficiency limits its application in the complete ablation of malignant tumors. The combination of nanomedicine and engineered bacteria has attracted increasing attention owing to their striking synergistic effects in cancer treatment. Engineered bacteria that function as natural vehicles can effectively deliver nanomedicines to tumor sites. Moreover, bacteria provide an opportunity to enhance nanomedicines by modulating the TME and producing substrates to support nanomedicine-mediated anticancer reactions. Nanomedicine exhibits excellent optical, magnetic, acoustic, and catalytic properties, and plays an important role in promoting bacteria-mediated biotherapies. The synergistic anticancer effects of engineered bacteria and nanomedicines in cancer therapy are comprehensively summarized in this review. Attention is paid not only to the fabrication of nanobiohybrid composites, but also to the interpromotion mechanism between engineered bacteria and nanomedicine in cancer therapy. Additionally, recent advances in engineered bacteria-synergized multimodal cancer therapies are highlighted.

Christensenella minuta interacts with multiple gut bacteria.

Gut microbes form complex networks that significantly influence host health and disease treatment. Interventions with the probiotic bacteria on the gut microbiota have been demonstrated to improve host well-being. As a representative of next-generation probiotics, Christensenella minuta (C. minuta) plays a critical role in regulating energy balance and metabolic homeostasis in human bodies, showing potential in treating metabolic disorders and reducing inflammation. However, interactions of C. minuta with the members of the networked gut microbiota have rarely been explored. In this study, we investigated the impact of C. minuta on fecal microbiota via metagenomic sequencing, focusing on retrieving bacterial strains and coculture assays of C. minuta with associated microbial partners. Our results showed that C. minuta intervention significantly reduced the diversity of fecal microorganisms, but specifically enhanced some groups of bacteria, such as Lactobacillaceae. C. minuta selectively enriched bacterial pathways that compensated for its metabolic defects on vitamin B1, B12, serine, and glutamate synthesis. Meanwhile, C. minuta cross-feeds Faecalibacterium prausnitzii and other bacteria via the production of arginine, branched-chain amino acids, fumaric acids and short-chain fatty acids (SCFAs), such as acetic. Both metagenomic data analysis and culture experiments revealed that C. minuta negatively correlated with Klebsiella pneumoniae and 14 other bacterial taxa, while positively correlated with F. prausnitzii. Our results advance our comprehension of C. minuta's in modulating the gut microbial network. C. minuta disrupts the composition of the fecal microbiota. This disturbance is manifested through cross-feeding, nutritional competition, and supplementation of its own metabolic deficiencies, resulting in the specific enrichment or inhibition of the growth of certain bacteria. This study will shed light on the application of C. minuta as a probiotic for effective interventions on gut microbiomes and improvement of host health.

Identification of a microbial sub-community from the feral chicken gut that reduces Salmonella colonization and improves gut health in a gnotobiotic chicken model.

A complex microbial community in the gut may prevent the colonization of enteric pathogens such as Salmonella. Some individual or a combination of species in the gut may confer colonization resistance against Salmonella. To gain a better understanding of the colonization resistance against Salmonella enterica, we isolated a library of 1,300 bacterial strains from feral chicken gut microbiota which represented a total of 51 species. Using a co-culture assay, we screened the representative species from this library and identified 30 species that inhibited Salmonella enterica subspecies enterica serovar Typhimurium in vitro. To improve the Salmonella inhibition capacity, from a pool of fast-growing species, we formulated 66 bacterial blends, each of which composed of 10 species. Bacterial blends were more efficient in inhibiting Salmonella as compared to individual species. The blend that showed maximum inhibition (Mix10) also inhibited other serotypes of Salmonella frequently found in poultry. The in vivo effect of Mix10 was examined in a gnotobiotic and conventional chicken model. The Mix10 consortium significantly reduced Salmonella load at day 2 post-infection in gnotobiotic chicken model and decreased intestinal tissue damage and inflammation in both models. Cell-free supernatant of Mix10 did not show Salmonella inhibition, indicating that Mix10 inhibits Salmonella through either nutritional competition, competitive exclusion, or through reinforcement of host immunity. Out of 10 species, 3 species in Mix10 did not colonize, while 3 species constituted more than 70% of the community. Two of these species were previously uncultured bacteria. Our approach could be used as a high-throughput screening system to identify additional bacterial sub-communities that confer colonization resistance against enteric pathogens and its effect on the host.IMPORTANCESalmonella colonization in chicken and human infections originating from Salmonella-contaminated poultry is a significant problem. Poultry has been identified as the most common food linked to enteric pathogen outbreaks in the United States. Since multi-drug-resistant Salmonella often colonize chicken and cause human infections, methods to control Salmonella colonization in poultry are needed. The method we describe here could form the basis of developing gut microbiota-derived bacterial blends as a microbial ecosystem therapeutic against Salmonella.

Changes in the Effect of Tree Stand Competition on the Pinus sibirica Undergrowth during Postfire Successions in Mid-Taiga Birch Forests of the Urals

The effect of light and root competition of the tree stand on the growth of the Pinus sibirica Du Tour undergrowth in post-fire birch forests of different ages is investigated using the example of mid-taiga forests of the Middle Urals. The studies were carried out on the basis of a microecosystem approach, using indices of light competition of the tree stand (Ilsc), root competition of the tree stand (Irsc) and integral competition of the tree stand (Irlsc). At the stage of the 13-year-old young birch stand with almost full illumination, the main factor determining the growth and development of Pinus sibirica undergrowth is root competition for soil nutrition. In the 32-year-old middle-aged birch stand, a joint, almost identical, effect of the factors of light and root competition on the growth of Pinus sibirica undergrowth is observed. In the mature 70-yearold birch stand, the main factor, influencing the growth of Pinus sibirica undergrowth, is the level of interception of photosynthetically active radiation by its canopy (light competition) with root competition is not expressed. In our opinion, this is due to the adaptive abilities and characteristics of the soil nutrition of the Pinus sibirica undergrowth and a change in the degree of soil saturation with organic compounds during the development of the post-fire birch forest.

A critical role for iron and zinc homeostatic systems in the evolutionary adaptation of Escherichia coli to metal restriction.

Host nutritional immunity utilizes metal deprivation to help prevent microbial infection. To investigate bacterial adaptation to such restrictive conditions, we conducted experimental evolution with two metal sequestering agents. Ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine pentamethylene phosphonic acid (DTPMP) were selected as ligands because they differentially affect cellular levels of iron, manganese and zinc in Escherichia coli. Mutants of E. coli strain BW25113 were isolated after cultivation at sub-minimum inhibitory concentration (MIC) chelant levels and genetic changes potentially responsible for tolerance were identified by whole-genome sequencing. In EDTA-selected strains, mutations in the promoter region of yeiR resulted in elevated gene expression. The yeiR product, a zinc-specific metallochaperone, was confirmed to be primarily responsible for EDTA resistance. Similarly, in two of the DTPMP-selected strains, a promoter mutation increased expression of the fepA-entD operon, which encodes components of the ferric-enterobactin uptake pathway. However, in this case improved DTPMP tolerance was only detectable following overexpression of FepA or EntD in trans. Additional mutations in the cadC gene product, an acid-response regulator, preserved the neutrality of the growth medium by constitutively activating expression of the cadAB regulon. This study uncovers specific resistance mechanisms for zinc and iron starvation that could emerge by selection against host nutritional immunity or competition with heterologous metallophores. It also provides insight into the specific metals affected by these two widely used chelators critical for their antibacterial mode of action.

Nutritional competition within tumor microenvironment dictates anti-tumor immunity

Nutritional competition within tumor microenvironment dictates anti-tumor immunity

Symbiotic Wolbachia in mosquitoes and its role in reducing the transmission of mosquito-borne diseases: updates and prospects.

Mosquito-borne diseases such as malaria, dengue fever, West Nile virus, chikungunya, Zika fever, and filariasis have the greatest health and economic impact. These mosquito-borne diseases are a major cause of morbidity and mortality in tropical and sub-tropical areas. Due to the lack of effective vector containment strategies, the prevalence and severity of these diseases are increasing in endemic regions. Nowadays, mosquito infection by the endosymbiotic Wolbachia represents a promising new bio-control strategy. Wild-infected mosquitoes had been developing cytoplasmic incompatibility (CI), phenotypic alterations, and nutrition competition with pathogens. These reduce adult vector lifespan, interfere with reproduction, inhibit other pathogen growth in the vector, and increase insecticide susceptibility of the vector. Wild, uninfected mosquitoes can also establish stable infections through trans-infection and have the advantage of adaptability through pathogen defense, thereby selectively infecting uninfected mosquitoes and spreading to the entire population. This review aimed to evaluate the role of the Wolbachia symbiont with the mosquitoes (Aedes, Anopheles, and Culex) in reducing mosquito-borne diseases. Global databases such as PubMed, Web of Sciences, Scopus, and pro-Quest were accessed to search for potentially relevant articles. We used keywords: Wolbachia, Anopheles, Aedes, Culex, and mosquito were used alone or in combination during the literature search. Data were extracted from 56 articles' texts, figures, and tables of the included article.

In Situ Molecular Ecological Analyses Illuminate Distinct Factors Regulating Formation and Demise of a Harmful Dinoflagellate Bloom.

The development and demise of a harmful algal bloom (HAB) are generally regulated by multiple processes; identifying specific critical drivers for a specific bloom is important yet challenging. Here, we conducted a whole-assemblage molecular ecological study on a dinoflagellate bloom to address the hypothesis that energy and nutrient acquisition, defense against grazing and microbial attacks, and sexual reproduction are critical to the rise and demise of the bloom. Microscopic and molecular analyses identified the bloom-causing species as Karenia longicanalis and showed that the ciliate Strombidinopsis sp. was dominant in a nonbloom plankton community, whereas the diatom Chaetoceros sp. dominated the after-bloom community, along with remarkable shifts in the community structure for both eukaryotes and prokaryotes. Metatranscriptomic analysis indicated that heightened energy and nutrient acquisition in K. longicanalis significantly contributed to bloom development. In contrast, active grazing by the ciliate Strombidinopsis sp. and attacks by algicidal bacteria (Rhodobacteracea, Cryomorphaceae, and Rhodobacteracea) and viruses prevented (at nonbloom stage) or collapsed the bloom (in after-bloom stage). Additionally, nutrition competition by the Chaetoceros diatoms plausibly contributed to bloom demise. The findings suggest the importance of energy and nutrients in promoting this K. longicanalis bloom and the failure of antimicrobial defense and competition of diatoms as the major bloom suppressor and terminator. This study provides novel insights into bloom-regulating mechanisms and the first transcriptomic data set of K. longicanalis, which will be a valuable resource and essential foundation for further elucidation of bloom regulators of this and related species of Kareniaceae in the future. IMPORTANCE HABs have increasingly occurred and impacted human health, aquatic ecosystems, and coastal economies. Despite great efforts, the factors that drive the development and termination of a bloom are poorly understood, largely due to inadequate in situ data about the physiology and metabolism of the causal species and the community. Using an integrative molecular ecological approach, we determined that heightened energy and nutrient acquisition promoted the bloom, while resource allocation in defense and failure to defend against grazing and microbial attacks likely prevented or terminated the bloom. Our findings reveal the differential roles of multiple abiotic and biotic environmental factors in driving the formation or demise of a toxic dinoflagellate bloom, suggesting the importance of a balanced biodiverse ecosystem in preventing a dinoflagellate bloom. The study also demonstrates the power of whole-assemblage metatranscriptomics coupled to DNA barcoding in illuminating plankton ecological processes and the underlying species and functional diversities.

Effects of time-space conversion on microflora structure, secondary metabolites composition and antioxidant capacity of Codonopsis pilosula root

In order to study the relationship between medicinal plant Codonopsis pilosula phenotype, secondary metabolites, antioxidant capacity and its rhizosphere soil nutrients, root-related microorganisms under seasonal and geographical changes, high-throughput sequencing technology was used to explore the bacterial community structure and variation in rhizosphere soil and root endosphere from six regions of Dingxi City, Gansu Province during four seasons. Secondary metabolites composition and antioxidant capacities of C. pilosula root collected successively from four seasons were determined. The chemical properties, nutrient content and enzyme activities of rhizosphere of C. pilosula were significantly different under different temporal and spatial conditions. All soil samples were alkaline (pH 7.64–8.42), with water content ranging from 9.53% to 19.95%, and electrical conductivity varied widely, showing obvious time-scale effects. Different time scales were the main reasons for the diversity and structure of rhizosphere bacterial community of C. pilosula. The diversity and richness of rhizosphere bacterial community in autumn and winter were higher than those in spring and summer, and bacterial community structure in spring and summer was more similar to that in autumn and winter. The root length and diameter of C. pilosula showed significant time gradient difference under different spatiotemporal conditions. Nutrition and niche competition lead to significant synergistic or antagonistic interactions between rhizosphere bacteria and endophytic bacteria, which invisibly affect soil properties, abundance of functional bacteria and even yield and quality of C. pilosula. Soil properties, rhizosphere bacteria and endophytic bacteria directly promoted root phenotype, stress resistance and polysaccharide accumulation of C. pilosula.

Attenuating Metabolic Competition of Tumor Cells for Favoring the Nutritional Demand of Immune Cells by a Branched Polymeric Drug Delivery System.

Tumor cells are dominant in the nutritional competition in the tumor microenvironment, and their metabolic abnormalities often lead to microenvironmental acidosis and nutrient deprivation, thereby impairing the function of immune cells and diminishing the antitumor therapeutic effect. Herein, a branched polymeric conjugate and its efficacy in attenuating the metabolic competition of tumor cells are reported. Compared with the control nanoparticles prepared from its linear counterpart, the branched-conjugate-based nanoparticles can more efficiently accumulate in the tumor tissue and interfere with the metabolic processes of tumor cells to increase the concentration of essential nutrients and reduce the level of immunosuppressive metabolites in the TME, thus creating a favorable environment for infiltrated immune cells. Its combined treatment with an immune checkpoint inhibitor (ICI) achieves an enhanced antitumor effect. The work presents a promising approach for targeting metabolic competition in the TME to enhance the chemo-immunotherapeutic effect against cancers.

Suppression of Banana Fusarium Wilt Disease with Soil Microbial Mechanisms via Pineapple Rotation and Residue Amendment

The large outbreak of banana Fusarium wilt has become a bottleneck limiting the industry’s development, and crop rotation is a cost-effective and essential measure to overcome the obstacles of banana crop monoculture. The present work was carried out to explore the mechanisms of how changes in soil chemical properties and the reestablishment of soil microorganisms in high-incidence soils are affected by crop rotation and plant residue. In this study, pineapple–banana crop rotation and pineapple residue amendment were carried out to alleviate banana Fusarium wilt, and their effects on bacterial and fungal communities were analyzed using the MiSeq Illumina sequencing platform. Both pineapple–banana rotation and residue addition significantly reduced disease incidence. Moreover, pineapple rotation and residue amendment altered the bacterial and fungal community composition. The taxonomic and phylogenetic alpha diversity of bacteria and fungi significantly increased against disease suppression and nutrition competition. The relative abundances of the Burkholderia, Pseudomonas, Elaphocordyceps, Penicillium, and Talaromyces genera were higher, and the number of Fusarium was significantly lower in rotational soil than in banana monoculture soil. Finally, linear models (LM) showed that the Burkholderia and Talaromyces in crop rotation, and Aspergillus in residue amendment had a significantly negative relationship to disease incidence, which plays a key role in Fusarium reduction. To consider the economic benefits and protect the vitality of the soil, this study suggested that pineapple–banana rotation and pineapple residue amendment both could be considered for the sustainable management of banana wilt.

127. Antimicrobial Efficacy Against Antibiotic-Tolerant Staphylococcus aureus Depends on the Mechanism of Antibiotic Tolerance

Abstract Background Bacteria can adopt an alternate metabolic state favoring small molecule synthesis over growth. In Staphylococcus aureus this is induced by factors present during infection including nutritional limitation and competition with other bacteria. Isogenic “tolerant” subpopulations have variable responses to antibiotics and can remain viable. Survivors resume growth upon cessation of antibiotics and cause relapse or recurrent infection. In this study we compare the capability of antibiotics to reduce viability of S. aureus made tolerant by different mechanisms. Methods Overnight cultures of S. aureus SH1000 were diluted to 106 cfu/mL. Tolerance was induced with mupirocin or 2-n-heptyl-4-hydroxypuinoline N-oxide (HQNO) simulating nutritional or competitive tolerance, respectively. Tolerant cultures were exposed to ceftaroline, daptomycin, gentamicin, levofloxacin, oritavancin or vancomycin at physiological concentrations and viability assessed by dilution plating. Minimum duration for 3-log viability reduction (“bactericidal activity”, MDK99.9) and 24h viability reduction were calculated independently for each of three biological replicates. Significance (P < 0.05) was determined using Student’s t-test. Results Time to bactericidal activity was prolonged for all antibiotics tested against nutritionally-tolerant S. aureus. Time to bactericidal activity was similarly prolonged against competitively-tolerant S. aureus, although the MDK99.9 of oritavancin was not affected. Viability reduction was mitigated for all antibiotics tested against nutritionally-tolerant S. aureus with the exception of oritavancin. In contrast, 24h viability reduction of competitively-tolerant S. aureus only occurred with ceftaroline, gentamicin and vancomycin while daptomycin, levofloxacin and oritavancin remained equally potent. Conclusion Tolerance can alter both the time to bactericidal effect and the extent of killing. Both the antibiotic and the mechanism of tolerance impact time to bacterial effect and extent of killing. Oritavancin was the only antibiotic that maintained the same extent of killing regardless of tolerance mechanism. Further studies to evaluate additional antistaphylococcal antibiotics and different inducers of tolerance are warranted. Disclosures All Authors: No reported disclosures.

Antimicrobial Efficacy against Antibiotic-Tolerant Staphylococcus aureus Depends on the Mechanism of Antibiotic Tolerance.

Bacteria can adapt to a changing environment by adopting alternate metabolic states favoring small molecule synthesis and resilience over growth. In Staphylococcus aureus, these states are induced by factors present during infection, including nutritional limitations, host responses and competition with other bacteria. Isogenic "tolerant" populations have variable responses to antibiotics and can remain viable. In this study, we compared the capability of antibiotics to reduce the viability of S. aureus made tolerant by different mechanisms. Tolerance was induced with mupirocin, HQNO, peroxynitrite or human serum. Tolerant cultures were exposed to ceftaroline, daptomycin, gentamicin, levofloxacin, oritavancin or vancomycin at physiological concentrations, and the viability was assessed by dilution plating. The minimum duration for 3-log viability reduction and 24 h viability reduction were calculated independently for each of three biological replicates. Each tolerance mechanism rendered at least one antibiotic ineffective, and each antibiotic was rendered ineffective by at least one mechanism of tolerance. Further studies to evaluate additional antibiotics, combination therapy and different tolerance inducers are warranted.