Profiling Cellulolytic Bacteria Isolated from Tropical Atlantic Ocean Coastal Sediment in Escravos, Nigeria

Background: Marine sediments contain diverse, underexplored cellulose-degrading bacteria important for nutrient cycling. Coastal tropical regions, in particular, may offer promising strains for biotechnological applications. Aims: A diversity of microorganisms inhabits the marine environment. These organisms including cellulolytic bacteria can be useful in biotechnological applications. This study was therefore undertaken to ascertain the presence and identity of cellulose-degrading bacteria in Nigerian coastal sediments. Study Design: Laboratory tests were designed to isolate and identify cellulose-degrading bacteria from sediment and wood samples collected from the coastline of Escravos, Nigeria. Place and Duration of Study: The study was undertaken over a period of 6 months (April-September, 2024) using the Microbiology laboratory of Delta State University, Abraka, Nigeria. Methodology: Carboxyl Methyl Cellulose (CMC) and microcrystalline (MCC) agar were used to isolate cellulolytic bacteria and determine their cellulolytic index (CI) under aerobic and anaerobic conditions. Identification of isolates was by morphological, biochemical and molecular tests. Results: The cellulolytic bacterial isolates were 52 with 22 and 30 isolated under aerobic and anaerobic conditions, respectively. The isolates belong to the genera Bacillus, Pseudomonas, Klebsiella, Clostridium and Staphylococcus. Cellulolytic clearance diameter of the isolates on seawater CMC agar did not differ from those on mineral salts CMC agar under aerobic condition except Klebsiella (P=0.025). Anaerobically, clearance zones on the two media differed (P=0.029) with respect to Staphylococcus and Pseudomonas only. Bacillus was the most prevalent (40.4%) and also had the highest CI of 3.2-3.5; others had <2.0. The CI of all isolates in CMC differed significantly (P=0.000-0.020) from that of MCC except Bacillus. Molecular characterization of the Bacillus isolates as the most prevalent and cellulolytic confirmed them as Bacillus cereus (S2_907R_G08_20.ab1), Bacillus sanguinis (S6_907R_B09_06.ab1), Bacillus albus (S7_907R_C09_09.ab1), Bacillus thuringiensis (S8_907R_D09_12.ab1), Lysinibacillus fusiformis (S1_907R_F08_17.ab1), Lysinibacillus boronitolerans (S3_907R_H08_23.ab1), Lysinibacillus sphaericus (S5_907R_A09_03.ab1) and Lysinibacillus xylanilyticus (S10_907R_E09_15.ab1). CI of Bacillus and Lysinibacillus species varied, but were not markedly different. Conclusion: Bacillus and Lysinibacillus were the dominant cellulolytic bacteria in the coastal sediment. Their cellulolytic capabilities can be potentially useful in biotechnological applications.