58 research outputs found
Characterization of an alpha-L-fucosidase from the periodontal pathogen Tannerella forsythia
The periodontal pathogen Tannerella forsythia expresses several glycosidases which are linked to specific growth requirements and are involved in the invasion of host tissues. Ī±-l-Fucosyl residues are exposed on various host glycoconjugates and, thus, the Ī±-l-fucosidases predicted in the T. forsythia ATCC 43037 genome could potentially serve roles in host-pathogen interactions. We describe the molecular cloning and characterization of the putative fucosidase TfFuc1 (encoded by the bfo_2737 = Tffuc1 gene), previously reported to be present in an outer membrane preparation. In terms of sequence, this 51-kDa protein is a member of the glycosyl hydrolase family GH29. Using an artificial substrate, p-nitrophenyl-Ī±-fucose (KM 670 Ī¼M), the enzyme was determined to have a pH optimum of 9.0 and to be competitively inhibited by fucose and deoxyfuconojirimycin. TfFuc1 was shown here to be a unique Ī±(1,2)-fucosidase that also possesses Ī±(1,6) specificity on small unbranched substrates. It is active on mucin after sialidase-catalyzed removal of terminal sialic acid residues and also removes fucose from blood group H. Following knock-out of the Tffuc1 gene and analyzing biofilm formation and cell invasion/adhesion of the mutant in comparison to the wild-type, it is most likely that the enzyme does not act extracellularly. Biochemically interesting as the first fucosidase in T. forsythia to be characterized, the biological role of TfFuc1 may well be in the metabolism of short oligosaccharides in the periplasm, thereby indirectly contributing to the virulence of this organism. TfFuc1 is the first glycosyl hydrolase in the GH29 family reported to be a specific Ī±(1,2)-fucosidase
Macromolecular Fingerprinting of Sulfolobus Species in Biofilm: A Transcriptomic and Proteomic Approach Combined with Spectroscopic Analysis
Microorganisms in nature often live in surfaceassociated
sessile communities, encased in a self-produced
matrix, referred to as biofilms. Biofilms have been well studied in
bacteria but in a limited way for archaea. We have recently characterized
biofilm formation in three closely related hyperthermophilic
crenarchaeotes: Sulfolobus acidocaldarius, S. solfataricus, and
S. tokodaii. These strains form different communities ranging
from simple carpet structures in S. solfataricus to high density
tower-like structures in S. acidocaldarius under static condition.
Here, we combine spectroscopic, proteomic, and transcriptomic
analyses to describe physiological and regulatory features
associated with biofilms. Spectroscopic analysis reveals that in
comparison to planktonic life-style, biofilm life-style has distinctive
influence on the physiology of each Sulfolobus spp.
Proteomic and transcriptomic data show that biofilm-forming
life-style is strain specific (eg ca. 15% of the S. acidocaldarius
genes were differently expressed, S. solfataricus and S. tokodaii
had ā¼3.4 and ā¼1%, respectively). The -omic data showed that regulated ORFs were widely distributed in basic cellular functions,
including surface modifications. Several regulated genes are common to biofilm-forming cells in all three species. One of the most
striking common response genes include putative Lrs14-like transcriptional regulators, indicating their possible roles as a key
regulatory factor in biofilm development
Chirality of Matter Shows Up via Spin Excitations
Right- and left-handed circularly polarized light interact differently with
electronic charges in chiral materials. This asymmetry generates the natural
circular dichroism and gyrotropy, also known as the optical activity. Here we
demonstrate that optical activity is not a privilege of the electronic charge
excitations but it can also emerge for the spin excitations in magnetic matter.
The square-lattice antiferromagnet BaCoGeO offers an ideal arena to
test this idea, since it can be transformed to a chiral form by application of
external magnetic fields. As a direct proof of the field-induced chiral state,
we observed large optical activity when the light is in resonance with spin
excitations at sub-terahertz frequencies. In addition, we found that the
magnetochiral effect, the absorption difference for the light beams propagating
parallel and anti-parallel to the applied magnetic field, has an exceptionally
large amplitude close to 100%. All these features are ascribed to the
magnetoelectric nature of spin excitations as they interact both with the
electric and magnetic components of light
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