Picobenthic cyanobacterial populations revealed by 16S rRNA-targeted in situ hybridization.
We report on the morphological identification of a population of benthic cyanobacteria from microbial mats, known previously only from molecular analyses of field samples, based on the retrieval of environmental 16S rRNA sequences. We used in situ hybridization with horseradish peroxidase-labelled oligonucleotide probes designed to target the 16S rRNA of our unidentified population. Two probes were designed and checked for target binding ability and specificity using membrane hybridization against electroblotted bands from a denaturant gradient gel electrophoresis (DGGE) fingerprint of 16S rDNA gene fragments from the original cyanobacterial community. Under in situ hybridization, these probes bound specifically to extremely small, unicellular, colony-forming cyanobacteria, 0.75-1 microm in diameter, which were embedded in abundant mucilaginous investments. We propose the term picobenthos, by analogy with picoplankton, to describe those unicellular benthic microbes around or less than 1 microm in diameter. Although picoplanktonic cyanobacteria are abundant in ocean and freshwaters, picobenthic (<1 microm) unicellular cyanobacteria are not typically recognized as a major component of microbial mats. The small size and low levels of photopigment autofluorescence from these cells probably rendered them cryptic or indistinguishable from heterotrophic bacteria in routine microscopic observations. It is not known how widespread picobenthic cyanobacteria may be in other environments.
Max-Planck Institute for Marine Microbiology, Celsiusstrasse1, D-28359 Bremen, Germany. rabed@mpi-bremen.de
Raeid M M
RM
Abed
Wilhelm
W
Schönhuber
Rudolf
R
Amann
Ferran
F
Garcia-Pichel
D015373:Bacterial Typing Techniques; D003470:Culture Media; D000458:Cyanobacteria / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification / Q000648:ultrastructure; D015342:DNA Probes; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004275:DNA, Ribosomal / Q000032:analysis / Q000235:genetics; D020459:Genes, rRNA; D006735:Horseradish Peroxidase; D017403:In Situ Hybridization / Q000379:methods*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012965:Sodium Chloride; D014871:Water Microbiology
D003470:Culture Media; D015342:DNA Probes; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012965:Sodium Chloride; D006735:Horseradish Peroxidase