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Published on: February 22, 2017
Apolipoprotein A-I from striped bass (Morone saxatilis) demonstrates antibacterial activity in vitro
L Danielle Johnston1, Gwynne Brown, David Gauthier
1Virginia Institute of Marine Science, College of William and Mary, 1208 Greate Road, Gloucester Point, Virginia 23062, United States. dani_johnston@mac.com
Abstract:
HDL and apolipoprotein A-I from teleostean fishes demonstrate in vitro activity against gram-positive and gram-negative bacteria. In this study, we purified ApoA-1 from striped bass (Morone saxatilis) plasma and examined its in vitro antibacterial activity against Streptococcus sp., Escherichia coli, and Mycobacterium marinum. In addition, we obtained sequence for a putative striped bass ApoA-1 gene, which when translated contained the identical sequence generated from N-terminal sequencing of the purified ApoA-1. The predicted secondary and tertiary structures contained the characteristic proline residues and high alpha-helical content conserved between mammals and fishes. Purified ApoA-1 exhibited antibacterial activity against the bacteria assayed. Concentrations of 125 microg/mL for E. coli, 250 microg/mL for Streptococcus sp., and 250 microg/mL for M. marinum, inhibited bacterial growth by 50% compared to control. ApoA-1 plasma concentrations in experimental and wild fish ranged from undetectable levels to greater than 5 mg/mL, indicating that striped bass ApoA-1 is an effective antibacterial agent at concentrations below the range of physiological concentrations in striped bass plasma. We therefore conclude that ApoA-1 could play a role in innate defense against bacterial pathogens in striped bass.
Insights
Striped bass apolipoprotein A-I (ApoA-1) shows potent in vitro antibacterial activity against common pathogens like E. coli and Streptococcus sp. This fish protein functions effectively at concentrations below its natural physiological levels, suggesting a role in innate immunity.
Area of Science:
- Comparative immunology
- Fish biology
- Antimicrobial peptides
Background:
- High-density lipoprotein (HDL) and apolipoprotein A-I (ApoA-1) from fish exhibit antibacterial properties.
- ApoA-1 is a key component of HDL and plays roles in lipid metabolism and innate immunity.
Purpose of the Study:
- To purify and characterize apolipoprotein A-I (ApoA-1) from striped bass (Morone saxatilis).
- To investigate the in vitro antibacterial activity of striped bass ApoA-1 against specific bacterial pathogens.
- To compare the effective antibacterial concentrations with physiological levels in striped bass.
Main Methods:
- Purification of ApoA-1 from striped bass plasma.
- N-terminal sequencing and gene sequencing to confirm ApoA-1 identity.
- In vitro antibacterial assays against Streptococcus sp., Escherichia coli, and Mycobacterium marinum.
- Determination of minimum inhibitory concentrations (MICs).
Main Results:
- Striped bass ApoA-1 was successfully purified and sequenced, showing conserved structural features with mammalian and fish ApoA-1.
- Purified ApoA-1 demonstrated significant in vitro antibacterial activity against all tested bacteria.
- Effective concentrations (125-250 µg/mL) were below the physiological range found in striped bass plasma (>5 mg/mL).
Conclusions:
- Striped bass ApoA-1 possesses potent antibacterial activity against Gram-positive and Gram-negative bacteria.
- ApoA-1 likely contributes to the innate immune defense system of striped bass against bacterial infections.
- The findings support the conserved role of ApoA-1 in host defense across vertebrate species.
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