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Electron microscopic examination of uncultured soil‐dwelling bacteria
Author(s) -
Amako Kazunobu,
Takade Akemi,
Taniai Hiroaki,
Yoshida Shinichi
Publication year - 2008
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.2008.00037.x
Subject(s) - bacteria , biology , nucleoid , cytoplasm , cell envelope , peptidoglycan , gram negative bacteria , archaea , bacterial cell structure , microbiology and biotechnology , electron microscope , gram positive bacteria , cell wall , botany , escherichia coli , biochemistry , genetics , physics , optics , gene
Bacteria living in soil collected from a rice paddy in Fukuoka, Japan, were examined by electron microscopy using a freeze‐substitution fixation method. Most of the observed bacteria could be categorized, based on the structure of the cell envelope and overall morphology, into one of five groups: (i) bacterial spore; (ii) Gram‐positive type; (iii) Gram‐negative type; (iv) Mycobacterium like; and (v) Archaea like. However, a few of the bacteria could not be readily categorized into one of these groups because they had unique cell wall structures, basically resembling those of Gram‐negative bacteria, but with the layer corresponding to the peptidoglycan layer in Gram‐negative bacteria being extremely thick, like that of the cortex of a bacterial spore. The characteristic morphological features found in many of these uncultured, soil‐dwelling cells were the nucleoid being in a condensed state and the cytoplasm being shrunken. We were able to produce similar morphologies in vitro using a Salmonella sp. by culturing under low‐temperature, low‐nutrient conditions, similar to those found in some natural environments. These unusual morphologies are therefore hypothesized to be characteristic of bacteria in resting or dormant stages.