Assessment of bacterial community structure in the deep sub-seafloor biosphere by 16S rDNA-based techniques: a cautionary tale

• Published in: Journal of microbiological methods Vol. 55; no. 1; pp. 155 - 164
• Main Authors: Webster, Gordon, Newberry, Carole J., Fry, John C., Weightman, Andrew J.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01-10-2003; Elsevier Science
• Subjects: 16S rRNA; Anaerobic sediments; Bacteria - isolation & purification; Biological and medical sciences; Deep biosphere; denaturing gradient gel electrophoresis; DGGE; DNA extraction; DNA, Bacterial - genetics; DNA, Ribosomal - genetics; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Geologic Sediments - microbiology; Marine; Microbiology; PCR bias; Polymerase Chain Reaction - methods; RNA, Ribosomal, 16S - genetics; Water Microbiology; I, Pacific; 16S rRNA; DNA extraction; Anaerobic sediments; Deep biosphere; DGGE; PCR bias; Polymerase chain reaction; Ribosomal DNA; 16S-RNA; Sediments; Microbial community
• ISSN: 0167-7012; 1872-8359
• DOI: 10.1016/S0167-7012(03)00140-4

Investigations into the deep marine environment have demonstrated the presence of a significant microbial biomass buried deep within sediments on a global scale. It is now believed that this deep biosphere plays a major role in the global cycling of elements and contains a large reservoir of organic carbon. This paper reports the development of a DNA extraction protocol that addresses the particular problems faced in applying molecular ecological techniques to samples containing very low biomass. Sediment samples were collected from different geographical locations within the Pacific Ocean and include the Ocean Drilling Program (ODP) Leg 190, Nankai Trough Accretionary Prism. Seven DNA extraction protocols were tested and a commercially available DNA extraction kit with modifications was shown to produce higher yields of polymerase chain reaction (PCR)-amplifiable DNA than standard laboratory methods. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene diversity revealed that template DNA from these extremely low biomass sediment samples was susceptible to PCR bias and random amplification. We propose that it is essential to screen 16S rRNA gene products for bacterial diversity by DGGE or other rapid fingerprinting methods, prior to their use in establishing a representative clone library of deep sub-seafloor bacteria. This represents a cautionary approach to analysis of microbial diversity in such sub-seafloor ecosystems.