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Autolysis of Bacterial Cells Leads to Formation of Empty Sheaths by Leptothrix spp.
Department of Material Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
Laboratory of Plant Pathology, Graduate School of Environmental Science, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
* Author to whom correspondence should be addressed.
Received: 3 April 2013; in revised form: 3 June 2013 / Accepted: 14 June 2013 / Published: 20 June 2013
Abstract: The aquatic, Fe-oxidizing bacteria Leptothrix spp. produce uniquely shaped extracellular sheaths composed of organic bacterial polymers encrusted with inorganic elements from its aquatic environments. At the initial stage of sheath formation, bacterial cells were aligned in the sheath, but later most sheaths became empty. Here, we studied the mechanism of sheath hollowing by examining an isolate of Leptothrix sp. strain OUMS1 cultured in either artificial medium or natural groundwater. After 3 days in the medium, most sheaths at the initial stage surrounded a line of live cells, while some cells in the line were dead regardless of their position in a sheath. In sheaths where cells and/or their remnants were barely distinguishable by differential interference contrast microscopy (DIC), a vital stain and a stain specific for nucleic acids occasionally revealed dead cells and/or nucleic acid remnants, while sheaths that lacked a positive response to these reagents looked transparent when viewed with DIC. In specimens cultured in the medium for 7 days, dead cells increased in number regardless of their position in the sheath. Almost the same phenomena occurred in specimens cultured in natural groundwater until day 7. Transmission electron microscopy (TEM) showed that cells degenerated, leading to autolysis of bacterial cells in the sheath. These observations led us to conclude that autolysis of bacterial cells could be a major cause of sheath hollowing.
Keywords: empty sheath; Leptothrix spp.; iron-oxidizing bacteria; autolysis; L/D and DAPI dual staining
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Suzuki, T.; Ishihara, H.; Toyoda, K.; Shiraishi, T.; Kunoh, H.; Takada, J. Autolysis of Bacterial Cells Leads to Formation of Empty Sheaths by Leptothrix spp.. Minerals 2013, 3, 247-257.
Suzuki T, Ishihara H, Toyoda K, Shiraishi T, Kunoh H, Takada J. Autolysis of Bacterial Cells Leads to Formation of Empty Sheaths by Leptothrix spp.. Minerals. 2013; 3(2):247-257.
Suzuki, Tomoko; Ishihara, Hiromichi; Toyoda, Kazuhiro; Shiraishi, Tomonori; Kunoh, Hitoshi; Takada, Jun. 2013. "Autolysis of Bacterial Cells Leads to Formation of Empty Sheaths by Leptothrix spp.." Minerals 3, no. 2: 247-257.