Journal of Environmental Biology

Diversity metrics for the evaluation of cultivable Actinobacterial variety from the limestone soils of the Cuddapah Basin

S. Meenakshi¹, J. Hiremath², M.P. Shilpa¹ and S. Shivaveerakumar¹*     

¹Department of Microbiology, Davangere University, Shivagangothri, Davanagere-577 007, India

²Department of Food Science and Nutrition, Khaja Banda Nawaz University, Kalaburagi-585 104, India

Received: 11 February 2026                   Revised: 01 June 2026                   Accepted: 23 July 2026

*Corresponding Author Email : shiv_math1984@yahoo.com                 *ORCiD: https://orcid.org/0000-0002-0907-5610

Abstract

Aim: Limestone ecosystems represent geochemically unique and underexplored habitats that can harbor specialized Actinobacteria with vital applications. The present study investigates the culturable actinobacterial diversity from limestone-embedded soil of the Cuddapah Basin, India.

Methodology: A total of 36 isolates were obtained on selective media and identified by 16S rRNA gene sequencing.

Results: Quarry A yielded five genera, dominated by Streptomyces (41.7% of isolates), whereas Quarry B harbored eight genera, with a strong dominance of Streptomyces (58.3%). Despite the differences in richness, both quarries exhibited comparable Shannon diversity values of 1.468 and 1.465, respectively. Only two genera (Streptomyces and Rhodococcus) were shared between the two quarries, resulting in a low Jaccard similarity index of 0.182, indicative of limited overlap in genus composition. The Bray-Curtis dissimilarity value of 0.611 further supports noticeable differences in genus-level abundance structure between the two-quarry sites, proving dissimilarities in genus typed between two samples. Phylogenetic analysis resolved all isolates into well-supported lineage that correspond to their respective genera, reflecting broad representation across the orders Streptomycetales, Micrococcales and Mycobacteriales.

Interpretation: This study presents the first report of actinomycetes isolated from limestone quarry and provides the first baseline of combining culturedependent isolation with quantitative diversity metrics to evaluate actinobacterial diversity from the Cuddapah Basin limestone ecosystems of Southern India.

Key words: Actinobacteria, Cuddapah Basin, Culturable diversity, Limestone soil, Streptomyces

Copyright © 2026 Triveni Enterprises. All rights reserved. No part of the Journal can be reproduced in any form without prior permission. Responsibility regarding the authenticity of the data, and the acceptability of the conclusions enforced or derived, rest completely with the author(s).