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. 2016 Feb 29:7:204.
doi: 10.3389/fmicb.2016.00204. eCollection 2016.

Coral-Associated Actinobacteria: Diversity, Abundance, and Biotechnological Potentials

Huda M Mahmoud  1 , Aisha A Kalendar  1
Affiliations

Coral-Associated Actinobacteria: Diversity, Abundance, and Biotechnological Potentials

Huda M Mahmoud et al. Front Microbiol. .

Abstract

Marine Actinobacteria, particularly coral-associated Actinobacteria, have attracted attention recently. In this study, the abundance and diversity of Actinobacteria associated with three types of coral thriving in a thermally stressed coral reef system north of the Arabian Gulf were investigated. Coscinaraea columna, Platygyra daedalea and Porites harrisoni have been found to harbor equivalent numbers of culturable Actinobacteria in their tissues but not in their mucus. However, different culturable actinobacterial communities have been found to be associated with different coral hosts. Differences in the abundance and diversity of Actinobacteria were detected between the mucus and tissue of the same coral host. In addition, temporal and spatial variations in the abundance and diversity of the cultivable actinobacterial communities were detected. In total, 19 different actinobacterial genera, namely Micrococcus, Brachybacterium, Brevibacterium, Streptomyces, Micromonospora, Renibacterium, Nocardia, Microbacterium, Dietzia, Cellulomonas, Ornithinimicrobium, Rhodococcus, Agrococcus, Kineococcus, Dermacoccus, Devriesea, Kocuria, Marmoricola, and Arthrobacter, were isolated from the coral tissue and mucus samples. Furthermore, 82 isolates related to Micromonospora, Brachybacterium, Nocardia, Micrococcus, Arthrobacter, Rhodococcus, and Streptomyces showed antimicrobial activities against representative Gram-positive and/or Gram-negative bacteria. Even though Brevibacterium and Kocuria were the most dominant actinobacterial isolates, they failed to show any antimicrobial activity, whereas less dominant genera, such as Streptomyces, did show antimicrobial activity. Focusing on the diversity of coral-associated Actinobacteria may help to understand how corals thrive under harsh environmental conditions and may lead to the discovery of novel antimicrobial metabolites with potential biotechnological applications.

Keywords: Arabian Gulf; Platygyra daedalea; antimicrobial ability; culturable coral-associated Actinobacteria; temporal and spatial variation.

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Figures

FIGURE 1
FIGURE 1
The abundance of culturable Actinobacteria in coral tissue (□) and mucus (formula image) samples collected from the inshore reef system of Qit’at Benaya on March 2008.
FIGURE 2
FIGURE 2
The identity and percentage of actinobacterial isolates obtained from (A)C. culumna tissue, (B)C. culumna mucus, (C)P. deadalea tissue, (D)P. deadalea mucus, (E)P. harrisoni tissue, and (F)P. harrisoni mucus collected from inshore reef system on March 2008.
FIGURE 3
FIGURE 3
The abundance of culturable Actinobacteria in coral tissue and mucus samples collected from the inshore reef system of Qit’at Benaya (formula image) and the offshore reef system of Umm Al-Maradim (□) on October 2008.
FIGURE 4
FIGURE 4
The identity and percentage of actinobacterial isolates obtained from (A)P. deadalea tissue (B)P. deadalea mucus from inshore reef system of Qit’at Benaya (C)P. deadalea tissue (D)P. deadalea mucus collected from offshore reef system of Umm Al-Maradim (October 2008).
FIGURE 5
FIGURE 5
The abundance of culturable Actinobacteria in Platygyra daedalea tissue (□) and mucus (formula image) samples collected from the inshore reef system of Qit’at Benaya on March 2009.
FIGURE 6
FIGURE 6
The identity and percentage of actinobacterial isolates obtained from (A)P. deadalea tissue (B)P. deadalea mucus from Qit’at Benaya inshore reef system (March 2009).
FIGURE 7
FIGURE 7
Antimicrobial activities for the actinobacterial isolates against three tested bacteria (i.e., Bacillus subtilis, Staphylococcus aureus, and Escherichia coli). All actinobacterial isolates showed strong antimicrobial activities with inhibition zones higher than 15 mm at least to one of the tested bacteria.
FIGURE 8
FIGURE 8
The percentage of actinobacterial isolates that showed antimicrobial activities against at least one of the utilized tested organisms (i.e., Bacillus subtilis, Staphylococcus aureus, and Escherichia coli).
See this image and copyright information in PMC

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