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The Type III Secreted Protein BopD in Bordetella bronchiseptica Is Complexed with BopB for Pore Formation on the Host Plasma Membrane. Hisashi Nogawa, 2004.The cytotoxicity of Bordetella bronchiseptica to infected cells is known to be dependent on a B . bronchiseptica type III secretion system . Although BopB, BopN, BopD, and Bsp22 have been identified as type III secreted proteins, these proteins remain to be characterized . In this study, in order to clarify the function of BopD during Bordetella infection, a BopD mutant was generated . Although secretion of BopD into the culture supernatant was completely abolished by the bopD mutation, the secretion of other type III secreted proteins was not affected by this mutation . It has been reported that severe cytotoxicity, including cell detachment from the substrata, and release of lactate dehydrogenase (LDH) into the supernatant are induced in L2 cells by wild-type B . bronchiseptica infection, and these phenotypes are dependent on the type III secretion system . In contrast, neither cell detachment nor LDH release was induced in L2 cells infected with the BopD mutant . Furthermore, the hemolytic activity of the BopD mutant was greatly impaired compared with that of the wild-type strain . On the basis of the results of coimmunoprecipitation assays with anti-BopB antibodies, we conclude that BopD has the ability to associate with BopB . Finally, we show that the BopD-BopB complex is responsible for the pore formation in the host plasma membrane that functions as the conduit for the transition of effector proteins into host cells . Ferrihydrite-Dependent Growth of Sulfurospirillum deleyianum through Electron Transfer via Sulfur Cycling. Kristina L. Straub, 2004.Observations in enrichment cultures of ferric iron-reducing bacteria indicated that ferrihydrite was reduced to ferrous iron minerals via sulfur cycling with sulfide as the reductant . Ferric iron reduction via sulfur cycling was investigated in more detail with Sulfurospirillum deleyianum, which can utilize sulfur or thiosulfate as an electron acceptor . In the presence of cysteine (0.5 or 2 mM) as the sole sulfur source, no (microbial) reduction of ferrihydrite or ferric citrate was observed, indicating that S . deleyianum is unable to use ferric iron as an immediate electron acceptor . However, with thiosulfate at a low concentration (0.05 mM), growth with ferrihydrite (6 mM) was possible and sulfur was cycled up to 60 times . Also, spatially distant ferrihydrite in agar cultures was reduced via diffusible sulfur species . Due to the low concentrations of thiosulfate, S . deleyianum produced only small amounts of sulfide . Obviously, sulfide delivered electrons to ferrihydrite with no or only little precipitation of black iron sulfides . Ferrous iron and oxidized sulfur species were produced instead, and the latter served again as the electron acceptor . These oxidized sulfur species have not yet been identified . However, sulfate and sulfite cannot be major products of ferrihydrite-dependent sulfide oxidation, since neither compound can serve as an electron acceptor for S . deleyianum . Instead, sulfur (elemental S or polysulfides) and/or thiosulfate as oxidized products could complete a sulfur cycle-mediated reduction of ferrihydrite . Effects of Minerals on Resistance of Bacillus subtilis Spores to Heat and Hydrostatic Pressure. Noriyuki Igura, 2003.Among Bacillus subtilis IFO13722 spores sporulated at 30, 37, and 44°C, those sporulated at 30°C had the highest resistance to treatments with high hydrostatic pressure (100 to 300 MPa, 55°C, 30 min) . Pressure resistance increased after demineralization of the spores and decreased after remineralization of the spores with Ca2+ or Mg2+, whereas the resistance did not change when spores were remineralized with Mn2+ or K+, suggesting that former two divalent ions were involved in the activation of cortex-lytic enzymes during germination .
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