Bacteriocin-like protein produced Brevibacillus laterosporus that can inhibit the growth of drug resistant bacteria

Currently, resistance of pathogenic organisms to approved antibiotics has become a worldwide problem with serious consequences on the treatment of infectious diseases [12]. The increased use/misuse of antibiotics in a treatment of infectious diseases is mainly causing to the phenomenon and/or pathogenic bacteria develop mechanism of antibiotic resistance [2]. There is an alarming increase of antibiotic resistance of bacteria that cause either community infections and/or hospital-acquired infections. Of particular interest are the multidrug resistant pathogens such as methicillinresistant Staphylococcus aureus (MRSA), vancomycin-resistant MRSA, penicillin-resistant Streptococcus pneumoniae (PRSP) and vancomycin-resistant Enterococcus (VRE) [3]. Including, ESBLs (extended-spectrum beta-lactamases)-producing strains such as Klebsiella pneumoniae, Pseudomonas aeruginosa and E. coli etc., which can be transferred antibiotic-resistant gene to the other species by conjugation [4]. In many multidrug resistant pathogens, MRSA and ESBLs-producing strains are the most serious pathogens because they are a major cause of nosocomial infections and non-hospital acquired infections that associated morbidity and mortality. In many years past, the emergence of MRSA strains resistant to all -lactam antibiotics. Since the discovery, development and drug administration approval of vancomycin in the 1950s, this antibiotic is a mainstay for the treatment of infections caused by MRSA. However, because of the development of new anti-staphylococcal antibiotics, several researches reported vancomycin failure [5-6]. The MRSA, ESBLs-producing strains and some multidrug resistant pathogen has multi-mechanism resistance such as 1) modifi cation of the bio-molecular target of antibiotics 2) enzymatic inactivation of antibiotic, e.g. -lactamases which hydrolyze -lactams 3) reduction of the intracellular antibiotic concentration in bacteria, by its effl ux outside from the cell through bacterial trans-membrane effl ux pumps. As a result, the development of novel antibiotics increases [2-3,7].


Introduction
Currently, resistance of pathogenic organisms to approved antibiotics has become a worldwide problem with serious consequences on the treatment of infectious diseases [1][2]. The increased use/misuse of antibiotics in a treatment of infectious diseases is mainly causing to the phenomenon and/or pathogenic bacteria develop mechanism of antibiotic resistance [2]. There is an alarming increase of antibiotic resistance of bacteria that cause either community infections and/or hospital-acquired infections. Of particular interest are the multidrug resistant pathogens such as methicillinresistant Staphylococcus aureus (MRSA), vancomycin-resistant MRSA, penicillin-resistant Streptococcus pneumoniae (PRSP) and vancomycin-resistant Enterococcus (VRE) [3]. Including, ESBLs (extended-spectrum beta-lactamases)-producing strains such as Klebsiella pneumoniae, Pseudomonas aeruginosa and E. coli etc., which can be transferred antibiotic-resistant gene to the other species by conjugation [4]. In many multidrug resistant pathogens, MRSA and ESBLs-producing strains are the most serious pathogens because they are a major cause of nosocomial infections and non-hospital acquired infections that associated morbidity and mortality. In many years past, the emergence of MRSA strains resistant to all -lactam antibiotics. Since the discovery, development and drug administration approval of vancomycin in the 1950s, this antibiotic is a mainstay for the treatment of infections caused by MRSA. However, because of the development of new anti-staphylococcal antibiotics, several researches reported vancomycin failure [5][6].
The MRSA, ESBLs-producing strains and some multidrug resistant pathogen has multi-mechanism resistance such as 1) modifi cation of the bio-molecular target of antibiotics 2) enzymatic inactivation of antibiotic, e.g. -lactamases which hydrolyze -lactams 3) reduction of the intracellular antibiotic concentration in bacteria, by its effl ux outside from the cell through bacterial trans-membrane effl ux pumps. As a result, the development of novel antibiotics increases [2][3]7].
The several researches reported antibacterial/antimicrobial peptides or bacteriocins were applied as model for the production of novel antibiotics [8][9]  of using the two substances in combination [8]. According to the research report in 2008, the partially bioactive compounds, which expected as bacteriocin, produced by Brev. laterosporus strain SA14 inhibit the growth of clinical strain of MRSA [10]. Whereas, the non-specifi c on targets of the bioactive compounds and/or partially bioactive compounds is a major disadvantage. The several researches reported the bioactive compounds and/or partially bioactive compounds produced by many strains of Brev. laterosporus, which are major proteins, were used to control Musca domestica, Aedes aegypti, Coleoptera, parasitic nematodes ova/larvae and mollusks [11][12].

Brevibacillus laterosporus
Brev. laterosporus, previously classifi ed as Bacillus laterosporus (B. laterosporus) [13], is a Gram-positive bacilli and an aerobic spore-forming bacterium characterized by the production of a typical canoe-shaped parasporal body (CSPB) which remains fi rmly attached to one side of the spore after lysis of the sporangium. As a pathogen against invertebrates, its toxic activities against parasitic nematodes ova/larvae [11].
Antagonistic compounds produced by bacteria from the genus Brevibacillus have also been studied [19]. The strains of Brevibacillus laterosporus are well known produced antibacterial and antifungal agents [10,[20][21][22]. The recently characterized Brev. laterosporus OSY-I1 produces brevibacillin, a 1583 Da antimicrobial lipopeptide with a linear structure containing 13 amino acids and a C6 fatty acid at the N-terminus [23].
Brevibacillin shows strong antimicrobial activity against some pathogenic and food-spoilage Gram-positive bacteria, particularly MRSA, Listeria monocytogenes and Bacillus cereus. In addition, some strains of Brev. laterosporus also produced the medically important substance such as spergualin, which is a new antitumor antibiotic [13], and bacithrocins A, B and C [14].

Bacteriocin and Bacteriocin produced by Brevibacillus sp.
Bacteriocins, antibacterial peptides, which are produced by bacteria as a defense mechanism in complex environments [17].
It is short-sequence peptides that categorized into different classes based on structural and functional characteristics as  [25,28,[30][31]. The mode of action of bacteriocins is most likely based on its amphiphilic nature and the ability of the cationic amino acids to interact with the negatively charged phospholipids of the cell membrane, causing the disruption and depolarization of the membrane [23]. A similar mechanism was observed in the case of paenibacterin, a broad-spectrum antimicrobial lipopeptide produced by Paenibacillus thiaminolyticus [32]. In addition, it was found that the marine bacterial isolate Brevibacillus laterosporus PNG-276 showed broad-spectrum antibiotic activity (producing polyketides the basiliskamides A and B and non-ribosomal peptides: loloatins A-D and bogorols A-E) against the human pathogens MRSA, VRE, Mycobacterium tuberculosis, Candida albicans, and Escherichia coli [33].
The laterosporulin, a novel bacteriocin produced by Brevibacillus laterosporus strain Gl-9 [34]., which are class IId bacteriocin because of molecular weight of peptide to be of 5.6 kDa. The open reading frame (ORF) encoding laterosporulin were identifi ed a 4 kb region from the draft genome sequence of Gl-9. The 4 kb region contained the putative structural gene encoding laterosporulin and its fl anking genes (transcriptional regulator, hypothetical protein, ABC transporter and alkyl hydroperoxide reductase). The ORF of 153 nucleotides followed the putative Shine-Dalgarno sequence most likely codes for the bacteriocins [17]. Laterosporulin is active against both Grampositive and Gram-negative bacteria and was found to be resistant to a range of proteolytic enzymes. Structural studies revealed that the peptide consists of twisted Antimicrobials from new Brevibacillus laterosporus strains [https://doi.org/10.1371/ journal.pone.0216773; 35]. -sheet and includes three disulfi de bonds [36]. Laterosporulin is relatively rich in cysteine and polar amino acids, which is atypical for bacteriocins in general, whereas its structure showed similarities with mammalian defensins. More recently, laterosporulin 10, produced by the strain Brevibacillus sp. SKDU10 was characterized [37] and, while considered similar, shows only 57.6% identity with laterosporulin. In addition, this novel bacteriocin has a different antimicrobial spectrum to laterosporulin as activity is limited to Gram-positive bacteria. However, laterosporulin 10 has also proven to be a promising new anti-cancer molecule that exhibits a cytotoxic effect on cancer cells [38].
The strains of Brev. laterosporus have been sequenced and and their genomes deposited in Genbank. These include LMG 15441 (under accession number AFRV00000000, [39]), GI-9 (under accession numbers CAGD01000001 to CAGD01000061, [40]), B9 (under accession numbers CP011074-CP011076, [41]), Lak 1210 (under accession number NDIP00000000, [42]), OSY-I1 (under accession number NOLX00000000, [43] bacteriocin-encoding genes will be inserted into appropriate shuttle / expression plasmid vector. The recombinant plasmids containing bacteriocin gene will be transferred to host cell-free protein expression system for introduce the novel bacteriocin production. With the hope, the constructed shuttle plasmid vector may be high segregational stability which can be introduce the novel bacteriocin production in large scale for industrial use.

Conclusion
It will be diffi cult to treat the drug resistant bacteria without increased funding for drug discovery. Bacteriocin producing bacteria are applicable used for treatment of infectious disease caused from drug resistant microorganisms. Though anti-drug resistant microorganisms MIC of bacteriocin is higher but they have resistance modifying properties. Therefore, bacteriocin derived drugs can help in fi ghting the drug resistance.