scholarly journals Bacterial Endophytes and Their Interactions with Hosts

2006 ◽  
Vol 19 (8) ◽  
pp. 827-837 ◽  
Author(s):  
Mónica Rosenblueth ◽  
Esperanza Martínez-Romero
Keyword(s):  
Defense Responses ◽  
Growth And Yield ◽  
Human Pathogens ◽  
Salmonella Spp ◽  
Bacterial Populations ◽  
Process Plant ◽  
Bacterial Mutants ◽  
Plant Genes ◽  
Colonization Process ◽  
Promote Plant Growth

Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seed-borne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endo-phytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.

scholarly journals Human Pathogens on Plants: Designing a Multidisciplinary Strategy for Research

2013 ◽  
Vol 103 (4) ◽  
pp. 306-315 ◽  
Author(s):  
Jacqueline Fletcher ◽  
Jan E. Leach ◽  
Kellye Eversole ◽  
Robert Tauxe
Keyword(s):  
Plant Pathology ◽  
Food Safety ◽  
Microbial Contamination ◽  
Management Strategies ◽  
Defense Responses ◽  
Plant Diseases ◽  
Food Microbiology ◽  
Food Plants ◽  
Human Pathogens ◽  
Salmonella Spp

Recent efforts to address concerns about microbial contamination of food plants and resulting foodborne illness have prompted new collaboration and interactions between the scientific communities of plant pathology and food safety. This article provides perspectives from scientists of both disciplines and presents selected research results and concepts that highlight existing and possible future synergisms for audiences of both disciplines. Plant pathology is a complex discipline that encompasses studies of the dissemination, colonization, and infection of plants by microbes such as bacteria, viruses, fungi, and oomycetes. Plant pathologists study plant diseases as well as host plant defense responses and disease management strategies with the goal of minimizing disease occurrences and impacts. Repeated outbreaks of human illness attributed to the contamination of fresh produce, nuts and seeds, and other plant-derived foods by human enteric pathogens such as Shiga toxin-producing Escherichia coli and Salmonella spp. have led some plant pathologists to broaden the application of their science in the past two decades, to address problems of human pathogens on plants (HPOPs). Food microbiology, which began with the study of microbes that spoil foods and those that are critical to produce food, now also focuses study on how foods become contaminated with pathogens and how this can be controlled or prevented. Thus, at the same time, public health researchers and food microbiologists have become more concerned about plant–microbe interactions before and after harvest. New collaborations are forming between members of the plant pathology and food safety communities, leading to enhanced research capacity and greater understanding of the issues for which research is needed. The two communities use somewhat different vocabularies and conceptual models. For example, traditional plant pathology concepts such as the disease triangle and the disease cycle can help to define cross-over issues that pertain also to HPOP research, and can suggest logical strategies for minimizing the risk of microbial contamination. Continued interactions and communication among these two disciplinary communities is essential and can be achieved by the creation of an interdisciplinary research coordination network. We hope that this article, an introduction to the multidisciplinary HPOP arena, will be useful to researchers in many related fields.

scholarly journals Bacteriophages: Combating Antimicrobial Resistance in Food-Borne Bacteria Prevalent in Agriculture

2021 ◽  
Vol 10 (1) ◽  
pp. 46
Author(s):  
Arnold Au ◽  
Helen Lee ◽  
Terry Ye ◽  
Uday Dave ◽  
Azizur Rahman
Keyword(s):  
Antimicrobial Resistance ◽  
Foodborne Pathogens ◽  
Phage Therapy ◽  
Human Pathogens ◽  
Salmonella Spp ◽  
Bacterial Populations ◽  
Bacterial Diseases ◽  
Agriculture Sector ◽  
Food Borne ◽  
Bactericidal Properties

Through recent decades, the subtherapeutic use of antibiotics within agriculture has led to the widespread development of antimicrobial resistance. This problem not only impacts the productivity and sustainability of current agriculture but also has the potential to transfer antimicrobial resistance to human pathogens via the food supply chain. An increasingly popular alternative to antibiotics is bacteriophages to control bacterial diseases. Their unique bactericidal properties make them an ideal alternative to antibiotics, as many countries begin to restrict the usage of antibiotics in agriculture. This review analyses recent evidence from within the past decade on the efficacy of phage therapy on common foodborne pathogens, namely, Escherica coli, Staphylococcus aureus, Salmonella spp., and Campylobacter jejuni. This paper highlights the benefits and challenges of phage therapy and reveals the potential for phages to control bacterial populations both in food processing and livestock and the possibility for phages to replace subtherapeutic usage of antibiotics in the agriculture sector.

scholarly journals Isolation and Characterization of Root-Associated Bacterial Endophytes and Their Biocontrol Potential against Major Fungal Phytopathogens of Rice (Oryza sativa L.)

Pathogens ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 172
Author(s):  
Maqsood Ahmed Khaskheli ◽  
Lijuan Wu ◽  
Guoqing Chen ◽  
Long Chen ◽  
Sajid Hussain ◽  
...  
Keyword(s):  
Oryza Sativa ◽  
Fungal Pathogens ◽  
Oryza Sativa L ◽  
Defense Responses ◽  
Growth And Yield ◽  
Bacterial Endophytes ◽  
16S Rrna Sequence ◽  
Resistance Response ◽  
Isolation And Characterization ◽  
Fungal Phytopathogens

Rice (Oryza sativa L.) is a major cereal food crop worldwide, and its growth and yield are affected by several fungal phytopathogens, including Magnaporthe oryzae, Fusarium graminearum, F. moniliforme, and Rhizoctonia solani. In the present study, we have isolated and characterized root-associated bacterial endophytes that have antifungal activities against rice fungal phytopathogens. A total of 122 root-associated bacterial endophytes, belonging to six genera (Bacillus, Fictibacillus, Lysinibacillus, Paenibacillus, Cupriavidus, and Microbacterium) and 22 species were isolated from three rice cultivars. Furthermore, the 16S rRNA sequence-based phylogeny results revealed that Bacillus was the most dominant bacterial genera, and that there were 15 different species among the isolates. Moreover, 71 root-associated endophytes showed antagonistic effects against four major fungal phytopathogens, including M. oryzae, F. graminearum, F. moniliforme, and R. solani. Additionally, the biochemical, physiological, and PCR amplification results of the antibiotic-related genes further supported the endophytes as potential biocontrolling agents against the rice fungal pathogens. Consequently, the findings in this study suggested that the isolated bacterial endophytes might have beneficial roles in rice defense responses, including several bioactive compound syntheses. The outcomes of this study advocate the use of natural endophytes as an alternative strategy towards the rice resistance response.

scholarly journals A METAGENOMIC ASSESSMENT OF BACTERIAL CONTAMINATION OF DUST EVENTS IN SENEGAL

2021 ◽  
Vol 9 (03) ◽  
pp. 509-526
Author(s):  
Alioune Marone ◽  
◽  
Malick Mbengue ◽  
Gregory Jenkins ◽  
Demba Ndao Niang ◽  
...  
Keyword(s):  
Respiratory Diseases ◽  
Rrna Gene ◽  
Source Population ◽  
Sequencing Analysis ◽  
Human Pathogens ◽  
Sequencing Data ◽  
Bacterial Populations ◽  
African Dust ◽  
Hypervariable Regions ◽  
Dust Events

Previous work in the Caribbean and West Africa have shown that air samples taken during dust events contain microorganisms (bacteria, fungi, viruses), including human pathogens that can cause many respiratory diseases. To better understand the potential downstream effect of bacteria dust on human health and public ecosystems, it is important to characterize the source population. In this study, we aimed to explore the bacterial populations of African dust samples collected between 2013-2017. The dust samples were collected using the spatula method, then the hypervariable regions (V3 and V4) of the 16S rRNA gene were amplified using PCR followed byMiSeq Illumina sequencing. Analysis of the sequencing data were performed using MG-RAST. At the phylum level, the proportions of Actinobacteria (22%), Firmicutes (20%), Proteobacteria (19%), and Bacteroidetes (13%) were respectively predominant in all dust samples. At the genus level, Bacillus(16%), Pseudomonas(10%), Nocardiodes and Exiguobacterium (5%) are the most dominated genera in African dust samples collected in this study.The study showed that molecular characterization of dust microbial population remains a very efficient method, also applicable to the search for viruses and fungi in this type of sample. It is important to note that the majority of microorganisms identified in this study can cause respiratory diseases.

Plant Resistance Genes for Fungal Pathogens - Physiological Models and Identification in Cereal Crops

1991 ◽  
Vol 46 (11-12) ◽  
pp. 969-981 ◽  
Author(s):  
Wolfgang Knogge
Keyword(s):  
Plant Defense ◽  
Resistance Genes ◽  
Fungal Pathogens ◽  
Plant Protection ◽  
Defense Responses ◽  
Avirulence Gene ◽  
Physiological Models ◽  
Plant Genes ◽  
Plant Pathogen Interaction

The complex biological phenomenon “resistance” can be reduced to single Mendelian traits acting on both the plant and the pathogen side in a number of pathosystems. According to the “gene-for-gene hypothesis”, the outcome of a plant/pathogen interaction in these cases is incompatibility if a plant carrying a particular resistance gene and a pathogen with the complementary avirulence gene meet. This suggests a causal role of resistance genes in a recognition process initiating active plant defense responses. Fundamentally different strategies are followed to identify these genes molecularly depending on the plant and pathogen species involved. Fungal diseases of crop plants, especially those of cereals, cause dramatic yield losses worldwide. It is assumed that a molecular characterization of plant genes conferring resistance to fungal pathogens will lead to a better understanding of the plant defense system in general permitting the development of new methods of crop plant protection.

scholarly journals Evaluation of a Steam Pasteurization Process in a Commercial Beef Processing Facility

1997 ◽  
Vol 60 (5) ◽  
pp. 485-492 ◽  
Author(s):  
ABBEY L. NUTSCH ◽  
RANDALL K. PHEBUS ◽  
M. JAMES RIEMANN ◽  
DAVID E. SCHAFER ◽  
J. E. BOYER ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Control Point ◽  
Meat Products ◽  
Steam Treatment ◽  
Salmonella Spp ◽  
Bacterial Populations ◽  
E Coli ◽  
Critical Control Point ◽  
Beef Processing ◽  
Steam Pasteurization

The effectiveness of a steam pasteurization process for reducing naturally occurring bacterial populations on freshly slaughtered beef sides was evaluated in a large commercial facility. Over a period of 10 days, 140 randomly chosen beef sides were microbiologically analyzed. Each side was sampled immediately before, immediately after, and 24 h after steam pasteurization treatment. Total aerobic bacteria (APC), Escherichia coli (generic), coliform, and Enterobacteriaceae populations were enumerated. The process significantly (P ≤ 0.01) reduced mean APCs from 2.19 log CFU/cm2 before treatment to 0.84 log CFU/cm2 immediately after and 0.94 log CFU/cm2 24 h after treatment. Before pasteurization (8 s steam exposure), 16.4% of carcasses were positive for generic E. coli (level of 0.60 to 1.53 log CFU/cm2), 37.9% were positive for coliforms (level of 0.60 to 2.26 log CFU/cm2), and 46.4% were positive for Enterobacteriaceae (level of 0.60 to 2.25 log CFU/cm2). After pasteurization, 0% of carcasses were positive for E. coli, 1.4% were positive for coliforms (level of 0.60 to 1.53 log CFU/cm2), and 2.9% were positive for Enterobacteriaceae (level of 0.60 to 1.99 log CFU/cm2). Of the 140 carcasses evaluated, one carcass was positive for Salmonella spp. before treatment (0.7% incidence rate); all carcasses were negative after steam treatment. This study indicates that steam pasteurization is very effective in a commercial setting for reducing overall bacterial populations on freshly slaughtered beef carcasses. The system may effectively serve as an important critical control point for HACCP systems at the slaughter phase of beef processing. In conjunction with other antimicrobial interventions (mandated by USDA to achieve zero tolerance standards for visible contamination) and good manufacturing practices, this process can play an important role in reducing the risk of pathogenic bacteria in raw meat and meat products.

scholarly journals Contact-Dependent Growth Inhibition in Bacteria: Do Not Get Too Close!

2020 ◽  
Vol 21 (21) ◽  
pp. 7990
Author(s):  
Larisa N. Ikryannikova ◽  
Leonid K. Kurbatov ◽  
Neonila V. Gorokhovets ◽  
Andrey A. Zamyatnin
Keyword(s):  
Signal Transduction ◽  
Growth Inhibition ◽  
Physical Contact ◽  
Ecological Niches ◽  
Competitive Advantages ◽  
Interspecies Interactions ◽  
Human Pathogens ◽  
Bacterial Populations ◽  
Dependent Growth ◽  
Contact Dependent Growth Inhibition

Over millions of years of evolution, bacteria have developed complex strategies for intra-and interspecies interactions and competition for ecological niches and resources. Contact-dependent growth inhibition systems (CDI) are designed to realize a direct physical contact of one bacterial cell with other cells in proximity via receptor-mediated toxin delivery. These systems are found in many microorganisms including clinically important human pathogens. The main purpose of these systems is to provide competitive advantages for the growth of the population. In addition, non-competitive roles for CDI toxin delivery systems including interbacterial signal transduction and mediators of bacterial collaboration have been suggested. In this review, our goal was to systematize the recent findings on the structure, mechanisms, and purpose of CDI systems in bacterial populations and discuss the potential biological and evolutionary impact of CDI-mediated interbacterial competition and/or cooperation.

Antagonistic Effect of Enterococcus faecium J96 against Human and Poultry Pathogenic Salmonella spp.

1999 ◽  
Vol 62 (7) ◽  
pp. 751-755 ◽  
Author(s):  
M. CARINA AUDISIO ◽  
GUILLERMO OLIVER ◽  
MARÍA C. APELLA
Keyword(s):  
Lactic Acid ◽  
Enterococcus Faecium ◽  
Intestinal Tract ◽  
Antagonistic Effect ◽  
Gram Negative Bacteria ◽  
Bactericidal Action ◽  
Human Pathogens ◽  
Salmonella Spp ◽  
Salmonella Serotypes ◽  
Free Ranging

Production of antagonistic compounds was studied in a strain of Enterococcus faecium isolated from the intestinal tract of a free-ranging chicken. Production of lactic acid and a bacteriocin was observed in cultures of this bacterium, alone and in mixed culture fermentations with pathogenic Salmonella serotypes (i.e., Gallinarum, Pullorum, Enteritidis, and Typhimurium). Growth inhibition of these avian and human pathogens was observed after 4 h of incubation at 37°C in CAm broth, a medium developed according to the nutrients present in chicken food. The antibacterial action was due to the combined effect of lactic acid and bacteriocin. Accumulation of these metabolites caused both a bacteriostatic and a bactericidal action against the gram-negative bacteria assayed.

scholarly journals Review of Phosphite as a Plant Nutrient and Fungicide

Soil Systems ◽  
2021 ◽  
Vol 5 (3) ◽  
pp. 52
Author(s):  
John L. Havlin ◽  
Alan J. Schlegel
Keyword(s):  
Nutritional Value ◽  
Genetic Manipulation ◽  
Growth And Yield ◽  
Plant Leaves ◽  
Negative Effects ◽  
Substantial Evidence ◽  
P Deficiency ◽  
Additional Information ◽  
Plant Genes ◽  
Anti Fungal

Phosphite (Phi)-containing products are marketed for their antifungal and nutritional value. Substantial evidence of the anti-fungal properties of Phi on a wide variety of plants has been documented. Although Phi is readily absorbed by plant leaves and/or roots, the plant response to Phi used as a phosphorus (P) source is variable. Negative effects of Phi on plant growth are commonly observed under P deficiency compared to near adequate plant P levels. Positive responses to Phi may be attributed to some level of fungal disease control. While only a few studies have provided evidence of Phi oxidation through cellular enzymes genetically controlled in plant cells, increasing evidence exists for the potential to manipulate plant genes to enhance oxidation of Phi to phosphate (Pi) in plants. Advances in genetic engineering to sustain growth and yield with Phi + Pi potentially provides a dual fertilization and weed control system. Further advances in genetic manipulation of plants to utilize Phi are warranted. Since Phi oxidation occurs slowly in soils, additional information is needed to characterize Phi oxidation kinetics under variable soil and environmental conditions.

scholarly journals Towards a better understanding of antimicrobial resistance dissemination: what can be learnt from studying model conjugative plasmids?

2022 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhen Shen ◽  
Christoph M. Tang ◽  
Guang-Yu Liu
Keyword(s):  
Antimicrobial Resistance ◽  
Rational Design ◽  
Global Public Health ◽  
Human Pathogens ◽  
Bacterial Populations ◽  
Gram Negative ◽  
Conjugative Plasmids ◽  
Defense Systems ◽  
Metabolic Properties ◽  
Gram Negative Organisms

AbstractBacteria can evolve rapidly by acquiring new traits such as virulence, metabolic properties, and most importantly, antimicrobial resistance, through horizontal gene transfer (HGT). Multidrug resistance in bacteria, especially in Gram-negative organisms, has become a global public health threat often through the spread of mobile genetic elements. Conjugation represents a major form of HGT and involves the transfer of DNA from a donor bacterium to a recipient by direct contact. Conjugative plasmids, a major vehicle for the dissemination of antimicrobial resistance, are selfish elements capable of mediating their own transmission through conjugation. To spread to and survive in a new bacterial host, conjugative plasmids have evolved mechanisms to circumvent both host defense systems and compete with co-resident plasmids. Such mechanisms have mostly been studied in model plasmids such as the F plasmid, rather than in conjugative plasmids that confer antimicrobial resistance (AMR) in important human pathogens. A better understanding of these mechanisms is crucial for predicting the flow of antimicrobial resistance-conferring conjugative plasmids among bacterial populations and guiding the rational design of strategies to halt the spread of antimicrobial resistance. Here, we review mechanisms employed by conjugative plasmids that promote their transmission and establishment in Gram-negative bacteria, by following the life cycle of conjugative plasmids.

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