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Journal of Bacteriology, January 2008, p. 555-563, Vol. 190, No. 2
0021-9193/08/$08.00+0     doi:10.1128/JB.01668-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

PhaP Is Involved in the Formation of a Network on the Surface of Polyhydroxyalkanoate Inclusions in Cupriavidus necator H16{triangledown}

Douglas Dennis,1* Vicki Sein,1 Edgar Martinez,1 and Brian Augustine2

Department of Integrated Natural Sciences, Arizona State University, Glendale, Arizona 85306,1 Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 228072

Received 15 October 2007/ Accepted 25 October 2007

Polyhydroxyalkanoate (PHA) inclusions are polymeric storage inclusions formed in some bacterial species when carbon levels are high but levels of another essential nutrient, such as nitrogen, are low. Though much is known about PHA synthesis, little is known about inclusion structure. In this study, atomic force microscopy (AFM) was employed to elucidate the structure of PHA inclusions at the nanoscale level, including the characterization of different layers of structure. AFM data suggest that underneath the inclusion envelope, there is a 2- to 4-nm-thick network layer that resides on top of a harder layer that is likely to be a crystalline lamellar polymer. The network is comprised of ~20-nm-wide linear segments and junctions that are typically formed by the joining of three to four of the linear segments. In some cases, ~50-nm globular structures that are raised ~1 to 2 nm above the network are present at the junctions. These globular structures always have a central pore that is ~15 nm in diameter. To determine if the major surface protein of PHA inclusions, PhaP, is involved in the structure of this network, inclusions from Cupriavidus necator H16 {Delta}phaP were examined. No network structure was detected. Instead, apparently random globular structures were found on the surfaces of the inclusions. When PhaP levels were reconstituted in this strain by the addition of phaP on a plasmid, the network was also reconstituted, albeit in a slightly different arrangement from that of the wild-type network. We conclude that PhaP participates in the formation of the inclusion network.

* Corresponding author. Mailing address: Department of Integrated Natural Sciences, Arizona State University West, P. O. Box 37100, Phoenix, AZ 85069-7100. Phone: (602) 543-6934. Fax: (602) 543-6073. E-mail: Douglas.dennis{at}asu.edu

{triangledown} Published ahead of print on 2 November 2007.

Journal of Bacteriology, January 2008, p. 555-563, Vol. 190, No. 2
0021-9193/08/$08.00+0     doi:10.1128/JB.01668-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Jendrossek, D. (2009). Polyhydroxyalkanoate Granules Are Complex Subcellular Organelles (Carbonosomes). J. Bacteriol. 191: 3195-3202 [Full Text]  


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