Abstract
Lignin, a characteristic component of terrestrial plants. Rivers transport large amounts of vascular plant organic matter into the oceans where lignin can degrade over time; however, microorganisms involved in this degradation have not been identified. In this study, several bacterial strains were isolated from marine samples using the lignin-derived compound vanillic acid (4-hydroxy-3-methoxybenzoic acid) as the sole carbon and energy source. The optimum growth temperature for all isolates ranged from 30 to 35°C. All isolates grew well in a wide NaCl concentration range of 0 to over 50 g/L, with an optimum concentration of 22.8 g/L, which is the same as natural seawater. Phylogenetic analysis indicates that these strains are the members of Halomonas, Arthrobacter, Pseudoalteromonas, Marinomonas, and Thalassospira. These isolates are also able to use other lignin-derived compounds, such as 4-hydroxybenzoic acid, ferulic acid, syringic acid, and benzoic acid. Vanillic acid was detected in all culture media when isolates were grown on ferulic acid as the sole carbon source; however, no 4-hydroxy-3-methoxystyrene was detected, indicating that ferulic acid metabolism by these strains occurs via the elimination of two side chain carbons. Furthermore, the isolates exhibit 3,4-dioxygenase or 4,5-dioxygenase activity for protocatechuic acid ring-cleavage, which is consistent with the genetic sequences of related genera. This study was conducted to isolate and characterize marine bacteria of degrading lignin-derived compounds, thereby revealing the degradation of aromatic compounds in the marine environment and opening up new avenues for the development and utilization of marine biological resources.
Highlights
Vanillic acid was used as lignin-derived low molecular weight compound to isolate vanillic acid-utilizing bacteria from marine and sediment samples collected from the coast of Lianyungang and the China East Sea, respectively
The predominant strains, which have adapted to their marine environment, could be isolated using the direct plating method, which resulted in isolation of bacteria with the highest growth rate in laboratory conditions
Vanillic acid was detected in all culture media when isolates were grown on ferulic acid as the sole carbon source; no 4-hydroxy-3-methoxystyrene was detected (Figs 5 and 6), indicating that ferulic acid metabolism by these strains occurs via the elimination of two side chain carbons
Summary
All experiments in the materials and methods were conducted according to protocols approved by Jiangsu Normal University and Anhui Normal University and completed by researchers of the manuscript. Field sampling is funded by the National Natural Science Foundation of China, and belongs to the research content of the project. The study area is not a special marine protected area and does not involve endangered or protected species. Seawater samples were collected from Lianyungang and sediments samples were collected from the East China Sea in Zhoushan, Zhejiang (30 ̊58020.71@N, 122 ̊ 95 41022.10@E), People’s. The depth of the sediment sample was 10 m below sea level, the water temperature was 20 ̊C. The sediments samples were placed in sealed plastic boxes surrounded with ice and brought to the laboratory within 24h
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