Bradyrhizobium japonicum FN1 produces an inhibitory substance that affects competition for nodule occupancy

Bacteriocins are narrow spectrum antibiotics of bacterial origin that can affect competition in resource-limited environments such as the rhizosphere. Therefore, bacteriocins may be good candidates for manipulation in order to generate more competitive inocula for soybean. In this study,<i> B. japonicum</i> FN1 along with other Bradyrhizobia in our culture collection were screened for bacteriocin-like activity. A total of five distinct inhibitory activities could be observed. FN1 genes putatively involved in bacteriocin production were computationally identified. These genes were mutagenized and the subsequent strains were screened for loss of inhibitory activity. Mutant strain BRJ-48, with an insert in<i> bjfn1_01204</i>, displayed a loss of the ability to inhibit an indicator strain. This loss could be complemented by the introduction of a plasmid expressing <i>bjfn1_01204 </i>in trans. The strain carrying the mutation did not affect competition in broth cultures, but was shown to be less competitive for nodule occupancy. Annotation suggests that <i>bjfn1_01204</i> encodes a carboxymuconolactone decarboxylase, however the direct contribution of how this enzyme contributes to inhibiting the tester strain remains unknown.

Screening and Evaluation of a Potential Bacteriocin Producing Lactobacillus in Milk and Dairy Products Collected from Puducherry

In an array of identifying safe antimicrobial compounds, bacteriocin producing Lactobacillus strain have been investigated in this study from the daily consuming food resources of humans. Till now, the best studied bacteriocins are nisin A produced by Lactobacillus lactis and pedocin PA-1 synthesized by Pediococcus acidilactici which have been accredited as a preservative in the food industries by the World Health Organization (WHO). For this study, four different milk and dairy products viz., curd, cheese, yoghurt and butter were collected from the local markets of Karaikal region, Puducherry, India and were used for the isolation of Lactobacillus species using MRS agar. Totally, five morphologically distinct strains were collected and were initially named as MPD 1 to MPD 5. During the screening process of bacteriocin production, the strain MPD 5 showed maximum antimicrobial activity against Vibrio cholerae MTCC 3906 with 900AU/ml. This strain was molecular identified as Lactiplantibacillus plantarum MDP 5 based on 16S rRNA partial sequence method. This 16S rRNA partial sequence was submitted to the NCBI nucleotide GenBank and provided with the accession number, MW301154.1. Further, this strain revealed an enhanced production of bacteriocin using the standardized physicochemical factors such as pH 7, 35°C, 2% fructose and 1% peptone. Furthermore, these optimal conditions revealed more than 2-fold increase in the bacteriocin production. All the above information suggesting the possibilities of bacteriocin for the bioindustrial production using the L. plantarum MDP 5 of this study and its future prospects for the investigation of biocidal activities against many highly infectious pathogens of human and veterinary.

Evolution of ColE1-like plasmids across γ-Proteobacteria: From bacteriocin production to antimicrobial resistance

Antimicrobial resistance is one of the major threats to Public Health worldwide. Understanding the transfer and maintenance of antimicrobial resistance genes mediated by mobile genetic elements is thus urgent. In this work, we focus on the ColE1-like plasmid family, whose distinctive replication and multicopy nature has given rise to key discoveries and tools in molecular biology. Despite being massively used, the hosts, functions, and evolutionary history of these plasmids remain poorly known. Here, we built specific Hidden Markov Model(HMM) profiles to search ColE1 replicons within genomes. We identified 1,035 ColE1 plasmids in five Orders of γ-Proteobacteria, several of which are described here for the first time. The phylogenetic analysis of these replicons and their characteristic MOBP5/HEN relaxases suggest that ColE1 plasmids have diverged apart, with little transfer across orders, but frequent transfer across families. Additionally, ColE1 plasmids show a functional shift over the last decades, losing their characteristic bacteriocin production while gaining several antimicrobial resistance genes, mainly enzymatic determinants and including several extended-spectrum betalactamases and carbapenemases. Furthermore, ColE1 plasmids facilitate the intragenomic mobilization of these determinants, as various replicons were identified co-integrated with large non-ColE1 plasmids, mostly via transposases. These results illustrate how families of plasmids evolve and adapt their gene repertoires to bacterial adaptive requirements.

DETECTION, OPTIMIZATION AND CHARACTERIZATION OF BACTERIOCIN PRODUCED BY LACTOBACILLUS FERMENTUM A STRAIN ISOLATED FROM HOME MADE CURD- INDIAN TRADITIONAL FOOD

Lactic acid bacteria display numerous antimicrobial activities mainly due to the production of bacteriocins and antifungal peptides. Bacteriocins are known for anti-microbial properties against various pathogens. The aim of this work is to investigate the effect of growth conditions on the maximum production of bacteriocin by Lactobacillus fermentum isolated from home made curd. Bacteriocin produced by Lactobacillus fermentum, inhibited the growth of Salmonella typhimurium, Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Proteus mirabilis. The exponential phase of the growth was started at 4h from the time of incubation. The stationary phase begins at the 12h from the time of incubation. Maximum bacteriocin production of 12650 AU/mL with more biomass was obtained in presence of glucose. Yeast extract as sole nitrogen source, in MRS broth, stimulated bacteriocin production upto 2400 AU/mL. The maximum bacteriocin production of 12200 AU/mL was obtained with 2 % of NaCl. The optimum pH for bacterial growth and bacteriocin production was identified as pH 5. The highest bacteriocin activity of 7250 AU/ml and maximum growth o of 1.90 was recorded at pH 5. Bacteriocin production was found to be highest at 40 C temperature (8100AU/ml). Optimization of bacteriocin production with the modification of environmental growth conditions will greatly benefit efficient commercial applications. The stability of the bacteriocin with respect to pH, temperature, enzyme sensitivity and organic solvents also studied.

Bacteriocin Production by Beta-Hemolytic Streptococci

Beta-hemolytic streptococci cause a variety of infectious diseases associated with high morbidity and mortality. A key factor for successful infection is host colonization, which can be difficult in a multispecies environment. Secreting bacteriocins can be beneficial during this process. Bacteriocins are small, ribosomally produced, antimicrobial peptides produced by bacteria to inhibit the growth of other, typically closely related, bacteria. In this systematic review, bacteriocin production and regulation of beta-hemolytic streptococci was surveyed. While Streptococcus pyogenes produces eight different bacteriocins (Streptococcin A-FF22/A-M49, Streptin, Salivaricin A, SpbMN, Blp1, Blp2, Streptococcin A-M57), only one bacteriocin of Streptococcus agalactiae (Agalacticin = Nisin P) and one of Streptococcus dysgalactiae subsp. equisimilis (Dysgalacticin) has been described. Expression of class I bacteriocins is regulated by a two-component system, typically with autoinduction by the bacteriocin itself. In contrast, a separate quorum sensing system regulates expression of class II bacteriocins. Both identified class III bacteriocins are plasmid-encoded and regulation has not been elucidated.

Transformation of Inferior Tomato into Preservative: Fermentation by Multi-Bacteriocin Producing Lactobacillus paracasei WX322

Loss and waste of postharvest vegetables are the main challenges facing the world’s vegetable supply. In this study, an innovative method of value-added transformation was provided: production of bacteriocin from vegetable waste, and then its application to preservation of vegetables. Antibacterial activity to soft rot pathogen Pectobacterium cartovorum (Pcb BZA12) indicated that tomato performed best in the nutrition supply for bacteriocin production among 12 tested vegetables. Moreover, the antibacterial activity was from Lactobacillus paracasei WX322, not components of vegetables. During a fermentation period of 10 days in tomato juice, L. paracasei WX322 grew well and antibacterial activity reached the maximum on the tenth day. Thermostability and proteinase sensitivity of the bacteriocin from tomato juice were the same with that from Man-Rogosa-Sharpe broth. Scanning electron microscope images indicated that the bacteriocin from tomato juice caused great damage to Pcb BZA12. At the same time, the bacteriocin from tomato juice significantly reduced the rotten rate of Chinese cabbage from 100% ± 0% to 20% ± 8.16% on the third day during storage. The rotten rate decrease of cucumber, tomato, and green bean was 100% ± 0% to 0% ± 0%, 70% ± 14.14% to 13.33% ± 9.43%, and 76.67% ± 4.71% to 26.67% ± 4.71%, respectively. Bacteriocin treatment did not reduce the rotten rate of balsam pear, but alleviated its symptoms.