Identification of a group D anti-lipopolysaccharide factor (ALF) from kuruma prawn (Marsupenaeus japonicus) with antibacterial activity against Vibrio parahaemolyticus

The effectiveness of gliding arc discharge plasma in sterilizing artificial seawater contaminated with Vibrio parahaemolyticus

The rapid proliferation of the halophilic pathogen Vibrio parahaemolyticus poses a severe health hazard to halobios and significantly impedes intensive mariculture. This study aimed to evaluate the potential application of gliding arc discharge plasma (GADP) to control the infection of Vibrio parahaemolyticus in mariculture. This study investigated the inactivation ability of GADP against Vibrio parahaemolyticus in artificial seawater (ASW), changes in the water quality of GADP-treated ASW, and possible inactivation mechanisms of GADP against Vibrio parahaemolyticus in ASW. The results indicate that GADP effectively inactivated Vibrio parahaemolyticus in ASW. As the volume of ASW increased, the time required for GADP sterilization also increased. However, the complete sterilization of 5000 mL of ASW containing Vibrio parahaemolyticus of approximately 1.0 × 104 CFU/mL was achieved within 20 min. Water quality tests of the GADP-treated ASW demonstrated that there were no significant changes in salinity or temperature when Vibrio parahaemolyticus (1.0 ×104 CFU/mL) was completely inactivated. In contrast to the acidification observed in plasma-activated water (PAW) in most studies, the pH of ASW did not decrease after treatment with GADP. The H2O2 concentration in the GADP-treated ASW decreased after post-treatment. The NO2-concentration in the GADP-treated ASW remained unchanged after post-treatment. Further analysis revealed that GADP induced oxidative stress in Vibrio parahaemolyticus, which increased cell membrane permeability and intracellular ROS levels of Vibrio parahaemolyticus. This study provides a viable solution for infection with the halophilic pathogen Vibrio parahaemolyticus and demonstrates the potential of GADP in mariculture.

Machine learning and genetic algorithm-guided directed evolution for the development of antimicrobial peptides

INTRODUCTION

Antimicrobial peptides (AMPs) are valuable alternatives to traditional antibiotics, possess a variety of potent biological activities and exhibit immunomodulatory effects that alleviate difficult-to-treat infections. Clarifying the structure-activity relationships of AMPs can direct the synthesis of desirable peptide therapeutics.

OBJECTIVES

In this study, the lipopolysaccharide-binding domain (LBD) was identified through machine learning-guided directed evolution, which acts as a functional domain of the anti-lipopolysaccharide factor family of AMPs identified from Marsupenaeus japonicus.

METHODS

LBDA-D was identified as an output of this algorithm, in which the original LBDMj sequence was the input, and the three-dimensional solution structure of LBDB was determined using nuclear magnetic resonance. Furthermore, our study involved a comprehensive series of experiments, including morphological studies and in vitro and in vivo antibacterial tests.

RESULTS

The NMR solution structure showed that LBDB possesses a circular extended structure with a disulfide crosslink at the terminus and two 310-helices and exhibits a broad antimicrobial spectrum. In addition, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that LBDB induced the formation of a cluster of bacteria wrapped in a flexible coating that ruptured and consequently killed the bacteria. Finally, coinjection of LBDB, Vibrio alginolyticus and Staphylococcus aureus in vivo improved the survival of M. japonicus, demonstrating the promising therapeutic role of LBDB for treating infectious disease.

CONCLUSIONS

The findings of this study pave the way for the rational drug design of activity-enhanced peptide antibiotics.

Comparative study of five anti-lipopolysaccharide factor genes in Litopenaeus vannamei

Anti-lipopolysaccharide factors (ALFs) are a family of common innate immune effectors in crustaceans, and they exhibit broad spectrum antimicrobial activity. In this study, we identified and characterized five novel ALF genes (designated as LvALF1-5) from the Pacific white shrimp (Litopenaeus vannamei) to investigate their potential immune functions. The amino acid sequence alignments showed that LvALFs contained two conserved cysteine residues, a hydrophobic N-terminal region, and the conserved signature sequence W(T/K)CPG(S)WT(A). They all shared high similarity with previously reported ALFs and were clearly novel members of the ALF family. The mRNA transcripts of LvALFs were most highly expressed in hemocytes and the hepatopancreas. After shrimp were stimulated with Vibrio parahaemolyticus or white spot syndrome virus, expression of the LvALFs was significantly induced in hemocytes and the hepatopancreas with various expression profiles. Recombinant proteins of LvALFs exhibited potent bacteriostatic activity in vitro. Together, these results suggest that LvALF1-5 participate in the immune response of Pacific white shrimp against invading pathogens.

Cloning and expression of two anti-lipopolysaccharide factors in Eriocheir hepuensis under Vibrio alginolyticus-induced stress

Anti-lipopolysaccharide factors (ALFs) are small basic proteins that exhibit broad-spectrum antiviral properties and antibacterial activity. In this research, we cloned and studied two Eriocheir hepuensis ALFs, EhALF2 and EhALF3. The results showed that the open reading frame lengths of EhALF2 and EhALF3 were 363 and 372 bp, encoding 120 and 123 amino acids, respectively. Their sequences both contained an Lipopolysaccharide-binding (LPS) domain and were highly similarity to other crab ALFs. qRT-PCR showed that EhALF2 and EhALF3 were detected in nine examined tissues and were expressed the highest in the haemocytes. After challenge with Vibrio alginolyticus, in the hepatopancreas, the expression levels of EhALF2 and EhALF3 reached the highest levels at 48 and 3 h, respectively. In the heart, the expression levels of the two genes were highest at 12 h. These results indicate that EhALF2 and EhALF3 could participate in the resistance of E. hepuensis to V. alginolyticus stress within a short time. They have potential applications in the study of environmental stress markers and disease-resistance factors in E. hepuensis.

The Multiple Influences of Natural Farming Environment on the Cultured Population Behavior of Kuruma Prawn, Penaeus japonicus

Recent years have witnessed a tremendous development in shrimp farming around the world, which, however, has raised a variety of issues, possibly due to a lack of knowledge of shrimp behavior in farms. This study focused on the relationship between shrimp behavior and the various factors of natural farming environment through situ surveys, as distinguished from the majority of laboratory studies on shrimp behavior. In the survey, the behaviors of kuruma prawn (Penaeus japonicus) were investigated in the groups of swimming in the water, crawling on the sand, resting on the sand, and hiding in the sand, followed by the quantification of the sex ratio, water quality, density, and light intensity. The results showed the average proportions of resting, hiding, crawling, and swimming activities of 69.87%, 20.85%, 8.24%, and 1.04%, respectively, of P. japonicus. The behavior of hiding, resting, and crawling is significantly affected by the sex ratio of the shrimp (p < 0.05). The proportions of hiding behavior exhibited a negative connection with density and a positive connection with light intensity, while the proportions of resting behavior showed the opposite according to both Pearson correlation analysis and multiple linear regression analysis. The light intensity was the only factor that significantly influenced the swimming behavior, in which the probability of the swimming behavior was reduced from 48% to 5% when light intensity varied from 0 to 10 lx, as determined by the generalized linear model. It could be speculated that P. japonicus prefers a tranquil environment. Female shrimp might exhibit less aggression and more adventure compared to male shrimp. The findings suggested light intensity, followed by density, as the most crucial element influencing the behavior of P. japonicus in the culture environment. These findings will contribute to the comprehension of the behavior of P. japonicus and provide a novel perspective for the formulation of its culture management strategy.

Marine Arthropods as a Source of Antimicrobial Peptides

Peptide therapeutics play a key role in the development of new medical treatments. The traditional focus on endogenous peptides has shifted from first discovering other natural sources of these molecules, to later synthesizing those with unique bioactivities. This review provides concise information concerning antimicrobial peptides derived from marine crustaceans for the development of new therapeutics. Marine arthropods do not have an adaptive immune system, and therefore, they depend on the innate immune system to eliminate pathogens. In this context, antimicrobial peptides (AMPs) with unique characteristics are a pivotal part of the defense systems of these organisms. This review covers topics such as the diversity and distribution of peptides in marine arthropods (crustacea and chelicerata), with a focus on penaeid shrimps. The following aspects are covered: the defense system; classes of AMPs; molecular characteristics of AMPs; AMP synthesis; the role of penaeidins, anti-lipopolysaccharide factors, crustins, and stylicins against microorganisms; and the use of AMPs as therapeutic drugs. This review seeks to provide a useful compilation of the most recent information regarding AMPs from marine crustaceans, and describes the future potential applications of these molecules.

Antibacterial activity of an anti-lipopolysaccharide factor (MjALF-D) identified from kuruma prawn (Marsupenaeus japonicus)

Antimicrobial peptides (AMPs) play important roles in host innate immune systems. Anti-lipopolysaccharide factor (ALF), which is a primary AMP in crustaceans, is active against bacteria, fungi and some viruses. MjALF-D, an anionic peptide, is a group D ALF isolated from Marsupenaeus japonicus. In the present study, a series of experiments were performed to study its antibacterial spectrum and further explore its antibacterial and bacterial binding activities. Liquid growth inhibition data demonstrated that recombinant MjALF-D (rMjALF-D) possessed strong antibacterial activity against the gram-positive bacterium Micrococcus luteus and the gram-negative bacterium Photobacterium damselae, with a minimum inhibitory concentration (MIC) or minimum bactericidal concentration (MBC) lower than 1.25 μM. The kinetic analysis showed that the antibacterial activity of rMjALF-D was dose- and time-dependent. Additionally, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations the potential bactericidal process. rMjALF-D treatment resulted in a large number of unidentified filamentous structures wrapped around the bacteria, and during the incubation, the cell surface became obviously rough and disrupted. rMjALF-D showed distinct binding ability after direct incubation with M. luteus and P. damselae but no binding ability to Escherichia coli, which was weakly inhibited by rMjALF-D. These data suggest that MjALF-D displays modest antibacterial activity and may provide more insights into the function and role of ALF in shrimp immunity.

BigPEN, an antimicrobial peptide of penaeidin family from shrimp Litopenaeus vannamei with membrane permeable and DNA binding activity

•

LvBigPEN, a member of penaeidins from L. vannamei, was regulated by host AP-1 signaling pathway.

•

LvBigPEN could bind to both Gram-negative bacteria and Gram-positive bacteria.

•

LvBigPEN could destroy bacterial cells and bind to DNA.

•

LvBigPEN played an important role in defense against V. parahaemolyticus infection.

Penaeidins are members of an antimicrobial peptide (AMP) family that have broad anti-microbial activities only found in penaeid shrimps. The LvBigPEN, a member of penaeidins from shrimp Litopenaeus vannamei, has showed antiviral activity against white spot syndrome virus (WSSV) in our previous report. However, whether LvBigPEN possesses potential anti-bacterial activities is still unknown. Herein, we found that the LvBigPEN played an important role in restricting the infection of Vibrio parahaemolyticus, a natural and Gram-negative bacteria pathogen in shrimp. The transcription of LvBigPEN was strongly induced after V. parahaemolyticus challenge. RNA interference (RNAi) mediated knockdown of LvBigPEN showed that LvBigPEN had a potential antibacterial function against V. parahaemolyticus. Microorganism binding assays indicated that rLvBigPEN could bind to both Gram-negative bacteria and Gram-positive bacteria. Transmission electron microscopy (TEM) analysis showed its ability to destroy bacterial cells in vitro. Besides, in a gel retardation assay, rLvBigPEN could bind to plasmid DNA and bacteria (V. parahaemolyticus) genomic DNA in a concentration-dependent manner. Moreover, the AP-1 pathway could participate in the transcription of LvBigPEN by the dual luciferase reporter assays. Taken together, these results suggested that LvBigPEN possessed the antibacterial activity against V. parahaemolyticus and may be alternative agents for the prevention and treatment of diseases caused by V. parahaemolyticus.

iTRAQ and PRM-based comparative proteomic profiling in gills of white shrimp Litopenaeus vannamei under copper stress

Crustaceans are particularly sensitive to heavy metal pollution. Copper (Cu) is one of typical heavy metal pollutants in aquatic ecosystems. However, limited attention has been paid on the proteomic responses of shrimp under Cu stress. White shrimp Litopenaeus vannamei held in 5‰ seawater were exposed to 5 mg L^-1 Cu for 3 h, and the regulatory mechanism in the gills was elucidated using iTRAQ-based quantitative proteomics. The results showed that a total of 5034 proteins were identified, 385 differentially expressed proteins (DEPs), including 147 differentially up-regulated proteins (DUPs) and 238 differentially down-regulated proteins (DDPs) were found. Bioinformatics analysis indicated the DEPs responding to Cu stress mainly involved in cytoskeleton, immune response, stress response, protein synthesis, detoxification, ion homeostasis and apoptosis. Furthermore, we still performed PRM analysis on sarcoplasmic calcium binding protein (SCP), serine proteinase inhibitor B3 (SPIB3), C-type lectin 4 (CTL4), cathepsin L (CATHL), JHE-like carboxylesterase 1 (CXE1) and paramyosin (PMY), and biochemical analysis on Cu/Zn-superoxide dismutase (Cu/Zn-SOD) to validate the iTRAQ results, respectively. The present proteome analysis revealed that Cu stress disrupted the ion homeostasis and protein synthesis, and L.vannamei mainly regulates a series of molecular pathways which contained many key proteins involved in the immune process to protect the organism from Cu stress. Our data provides more insight about the underlying mechanisms that related to the stress response of Cu exposure in crustacean.