Bacterially mediated manganese(II) oxidation greatly affects the biogeochemical cycling of Mn and other elements. One species of bacteria that are capable of Mn(II) oxidation is the gamma-proteobacterium Pseudomonas putida GB-1. In this organism, Mn(II) oxidation begins in stationary phase on the outer surface of the cell, forming a layer of insoluble Mn(III,IV) oxides. A random transposon mutagenesis screen isolated 12 mutant strains of P. putida GB-1 that exhibited increased Mn(II) oxidation on solid media relative to wild type. In 8 out of the 12 strains, the transposon had inserted into a putative flagellar gene. Those 8 strains each had motility defects, thus the disrupted genes are part of the P. putida GB-1 flagellar regulon. The flagellar genes identified include putative structural components (FliC, FliD, FlgE, and FlgL) and regulatory proteins (FlgM and FleN). Deletion of either the FleN gene (fleN) or the overlapping gene fliA resulted in increased Mn(II) oxidation, while in-frame deletion of fliF, which encodes an essential component of the basal body, did not. In liquid media, the flagellar mutants exhibited delayed Mn(II) oxidation relative to wild type. These results suggest that bacterial Mn(II) oxidation is regulated in part by flagellar-mediated responses to the surface substrate.

Mercuric ions (Hg 2+ ) and methylmercury are major, human-generated, toxic contaminants present in fish and our waterways. Bacteria provide a means of bioremediation by taking up these compounds and reducing them to volatile, non-toxic, elemental mercury (Hg°). Three types of mercury/ methylmercury transporters have previously been identified: MerC, MerF and MerT. Each of these sets of homologues has distinct topologies. MerF proteins are characterized by a 2-transmembrane !-helical segment (TMS) topology; most MerTs have three TMSs, and MerCs have four TMSs. This report shows that MerT and MerF proteins are related by common descent and are similar in sequence throughout their first two TMSs. One of the MerF proteins is internally duplicated, generating a protein with four TMSs, while several MerT homologues bear a Cterminal extracytoplasmic Hg 2+ -binding MerP domain. MerPs are homologous to heavy metal-binding domains present in copper chaperone proteins, at the N-termini of mercuric reductases and in from one to six copies in heavy metal transporting P-type ATPases. Phylogenetic analyses reveal that mercuric ion transporters have been horizontally transferred with high frequency between bacteria. Some MerTs function with MerP receptors while others do not, and the MerP-dependent MerTs cluster separately from the MerP-independent MerTs on a phylogenetic tree. MerTs possessing a MerP appear to have co-evolved with their cognate receptors. Conserved sequence and motif analyses serve to define the mercuric transporter family fingerprints and allow prediction of specific subfunctions. This report provides the first detailed bioinformatic description of two apparently unrelated families of Hg 2+ uptake transporters. We propose that all members of these two families function by a simple channel-type mechanism to allow influx of Hg 2+ in response to the membrane potential in preparation for reduction and detoxification. This information should facilitate the exploitation of these transporters for purposes of microbial and phytobioremediation.

Synthetic polymers with well-defined structures allow the development of nanomaterials with additional functions beyond biopolymers. Herein, we demonstrate de novo design of star-shaped glycoligands to interact with hemagglutinin (HA) using well-defined synthetic polymers with the aim of developing an effective inhibitor for the influenza virus. Prior to the synthesis, the length of the star polymer chains was predicted using the Gaussian model of synthetic polymers, and the degree of polymerization required to achieve multivalent binding to three carbohydrate recognition domains (CRDs) of HA was estimated. The star polymer with the predicted degree of polymerization was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and 6′-sialyllactose was conjugated as the glycoepitope for HA. The designed glycoligand exhibited the strongest interaction with HA as a result of multivalent binding. This finding demonstrated that the biological function of the synthetic polymer could be controlled by precisely defining the polymer structures.

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