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<p>The Cochin Estuary (CE), a part of Vembanad Lake on India’s southwest coast, is a highly dynamic and productive estuarine system. Although several studies related to hydrobiology, benthos, and pollution aspects are available, studies based on deep core sediment samples are lacking. This study characterizes the culturable heterotrophic bacterial communities from surface (0.2&#xa0;cm) and bottom (250&#xa0;cm) layers of a sediment core, focusing on their extracellular enzyme production and antibiotic resistance profiles. Biochemical characterization and 16S&#xa0;rRNA gene sequencing revealed that members of the genus <i>Bacillus</i> (<i>Bacillus thaonhiensis, Bacillus safensis, Bacillus cereus, Bacillus toyonensis, Bacillus paralicheniformis, Bacillus altitudinis, Bacillus pseudomycoides, Bacillus wiedmannii, Bacillus velezensis),</i> along with <i>Brevibacillus invocatus, Paenibacillus alvei, Rossellomorea marisflavi, Priestia koreensis,</i> were present in the surface layer. In contrast, various species of <i>Pseudomonas</i> (<i>Pseudomonas toyotomiensis, Pseudomonas oleovorans, Pseudomonas alcaliphila</i>) and <i>Rheinheimera</i> species (<i>Rheinheimera pleomorphica, Rheinheimera aquimaris, Rheinheimera nanhaiensis</i>) were encountered in the deeper layer of the sediment, indicating a compositional shift from Bacillota to Pseudomonadota (Proteobacteria) with depth. Protease and lipase activity were often present in the bacterial isolates from the surface sediment, whereas bottom isolates showed higher amylase and protease production. Antibiotic susceptibility tests revealed multidrug resistance (MAR ≥ 0.45) among several <i>Bacillus</i>, <i>Pseudomonas</i>, and <i>Rheinheimera</i> strains, suggesting that estuarine sediments serve as a reservoir of antibiotic-resistant bacteria.</p>

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Culturable and functional diversity of heterotrophic bacteria of a sediment core from Cochin estuary

  • 期刊论文

  • 发表日期：

    2026年1月26日

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  • Sabira Abdul Kareem Punnorkodu,
  • Jasna Vijayan,
  • Jabir Thajudeen,
  • Soumya Kavya Bhavan,
  • Shahana Kabeer Saleena,
  • Sumayya Nellikakath Sainudheen,
  • Jesmi Yousuf,
  • Farsana Alangadan,
  • Athira Thundiparambil Venu,
  • Mohamed Hatha Abdulla Ammanamveetil

摘要

The Cochin Estuary (CE), a part of Vembanad Lake on India’s southwest coast, is a highly dynamic and productive estuarine system. Although several studies related to hydrobiology, benthos, and pollution aspects are available, studies based on deep core sediment samples are lacking. This study characterizes the culturable heterotrophic bacterial communities from surface (0.2 cm) and bottom (250 cm) layers of a sediment core, focusing on their extracellular enzyme production and antibiotic resistance profiles. Biochemical characterization and 16S rRNA gene sequencing revealed that members of the genus Bacillus (Bacillus thaonhiensis, Bacillus safensis, Bacillus cereus, Bacillus toyonensis, Bacillus paralicheniformis, Bacillus altitudinis, Bacillus pseudomycoides, Bacillus wiedmannii, Bacillus velezensis), along with Brevibacillus invocatus, Paenibacillus alvei, Rossellomorea marisflavi, Priestia koreensis, were present in the surface layer. In contrast, various species of Pseudomonas (Pseudomonas toyotomiensis, Pseudomonas oleovorans, Pseudomonas alcaliphila) and Rheinheimera species (Rheinheimera pleomorphica, Rheinheimera aquimaris, Rheinheimera nanhaiensis) were encountered in the deeper layer of the sediment, indicating a compositional shift from Bacillota to Pseudomonadota (Proteobacteria) with depth. Protease and lipase activity were often present in the bacterial isolates from the surface sediment, whereas bottom isolates showed higher amylase and protease production. Antibiotic susceptibility tests revealed multidrug resistance (MAR ≥ 0.45) among several Bacillus, Pseudomonas, and Rheinheimera strains, suggesting that estuarine sediments serve as a reservoir of antibiotic-resistant bacteria.