Novel endolysin from <i>Streptococcus iniae</i> -Specific Prophage Selectively Inhibits Target Bacteria
Bibliographic record
Abstract
IntroductionAquaculture is a rapidly growing food production industry worldwide and plays a fundamental role in supplying protein food sources.Due to the growing emphasis on the increasing world population, which is projected to reach 9.73 billion people by 2064 [1], aquaculture industry production is estimated to increase to 109 million tons by 2030 [2].Therefore, to meet the rising consumer demand, implementing intensive farming systems that boost fish production and enhance feed efficiency is advisable.Nonetheless, intensive farming systems can also create favorable conditions for pathogens, resulting in increased transmission and frequency of infections, as well as promoting the survival and virulence of these pathogens [3].Several pathogenic diseases are prevalent in aquaculture, including vibriosis (Vibrio alginolyticus, V. fluvialis, and V. parahaemolyticus), aeromoniasis (Aeromonas hydrophila and A. salmonicida), edwardsiellosis (Edwardsiella ictaluri and E. tarda), and streptococcosis (Streptococcus iniae, S. agalactiae, and S. parauberis).These pathogenic diseases not only result in high mortality rates and economic losses in the aquaculture industry but also facilitate the transmission of zoonotic bacteria, posing a critical threat to human health [4,5].Streptococcosis is a re-emerging bacterial disease in the aquaculture industry that threatens its development worldwide.Although various Streptococcus species, including S. iniae, S. agalactiae, S. parauberis, S. uberis, and S. dysgalactiae, are known to cause streptococcosis [5], S. iniae and S. agalactiae are the primary species responsible for streptococcosis in aquaculture.S. iniae is a gram-positive, spherical-or ovoid-shaped, facultative anaerobic bacterium that is β-hemolytic on 5% sheep blood agar [5].S. iniae infections have been reported in various fish species globally, including olive flounder (Paralichthys olivaceus), salmon (Salmo salar), gray mullet (Mugus cephalus), barramundi (Lates calcarifer), yellowtail (Seriola quinqueradiata), and red drum (Sciaenops ocellatus) [6].Fish infected with S. iniae exhibit various symptoms such as septicemia, meningitis, panophthalmitis, exophthalmia, corneal opacity, and lethargy, resulting in high levels of mortality and morbidity [6].Various antibiotics, including florfenicol, erythromycin, doxycycline, and oxytetracycline, have been used to control streptococcosis in aquaculture [5].However, the use of antibiotics to control bacterial infections in fish has Streptococcus iniae is a gram-positive, spherical-or ovoid-shaped, facultative anaerobic bacterium and is one of the major species causing streptococcosis, resulting in economic losses in aquaculture.Endolysins, peptidoglycan hydrolases produced by bacteriophages, are emerging as replacements for antibiotics due to their specific lytic activity against pathogens.This study aimed to develop a novel endolysin, SinLys1930, that specifically targets and kills S. iniae.The molecular and structural characteristics of SinLys1930 were predicted based on bioinformatic approaches.The lytic activity of SinLys1930 was evaluated against S. iniae KCTC 3657 under various conditions, including different dosages, pH levels, temperatures, NaCl concentrations, and metal ions, to identify the optimal conditions, and its effectiveness was further tested in sterilized seawater.The conserved domain analysis revealed that SinLys1930 possesses two enzymatically active domains (NlpC/P60 and glucosaminidase superfamilies) with two cell wall-binding domains (CW-7 superfamily) positioned between them.The lytic activity of SinLys1930 was highest at pH 6.0 to 6.5 and temperatures between 16 and 37°C, and it was maintained even under high NaCl concentration.SinLys1930 reduced the optical density of S. iniae in sterilized seawater by approximately 60% after incubation for 1 h.Therefore, SinLys1930 could potentially serve as an alternative to antibiotics for preventing streptococcosis caused by S. iniae in the aquaculture industry.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".