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Ribulose 1, 5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) is a globally significant biocatalyst that facilitates the removal and sequestration of CO 2 from the biosphere. Rubiscocatalyzed CO 2 reduction thus provides virtually all the organic carbon utilized by living organisms. Despite catalyzing the rate-limiting step of photosynthetic and chemoautotrophic CO 2 assimilation, Rubisco is markedly inefficient as the competition between O 2 and CO 2 for the same substrate limits the ability of aerobic organisms to obtain maximum amounts of organic carbon for CO 2 -dependent growth. Random and site-directed mutagenesis procedures were coupled with genetic selection to identify an "oxygen insensitive" mutant cyanobacterial (Synechococcus sp. strain PCC 6301) Rubisco that allowed for CO 2 -dependent growth of a host bacterium at an oxygen concentration that inhibited growth of the host containing wild-type Synechococcus Rubisco. The mutant substitution, A375V, was identified as an intragenic suppressor of D103V, a negative mutant enzyme incapable of supporting autotrophic growth. Ala-375 (Ala-378 of spinach Rubisco) is a conserved residue in all form I (plant-like) Rubiscos. Structure-function analyses indicate that the A375V substitution decreased the enzyme's oxygen sensitivity (and not CO 2 /O 2 specificity), possibly by rearranging a network of interactions in a fairly conserved hydrophobic pocket near the active site. These studies point to the potential of engineering plants and other significant aerobic organisms to fix CO 2 unfettered by the presence of O 2 .The Calvin-Benson-Bassham (CBB) reductive pentose phosphate pathway provides a way for many organisms to reduce carbon dioxide to organic carbon, a process that is vital for life on earth (1). Rubisco is the rate-limiting enzyme in this pathway, catalyzing the initial steps in both autotrophic carbon assimilation (CO 2 fixation or carboxylation) and photooxidative metabolism (O 2 fixation or oxygenation) via parallel reaction mechanisms that share a common acceptor intermediate, the enediol form of RuBP (2). Thus, in aerobic organisms, the promiscuity of this enediolate for both CO 2 and O 2 limits autotrophic CO 2 assimilation. Severe limitations imposed on the enzyme's efficiency, primarily due to the competition between CO 2 and O 2 at the same active site and the poor turnover rate, have prompted numerous studies directed towards improving the enzyme's net carboxylation efficiency (2). Thus, an increase

The flagellum, a rotary engine required for motility in many bacteria, plays key roles in gene expression. It has been known for some time that flagellar substructures serve as checkpoints that coordinate flagellar gene expression with assembly. Less well understood, however, are other more global effects on gene expression. For instance, the flagellum acts as a 'wetness' sensor in Salmonella typhimurium and as a mechanosensor in other bacteria. Additionally, it has been implicated in a variety of bacterial processes, including biofilm formation, pathogenesis and symbiosis. Although for many of these processes it may be simply that motility is required, for other cases it seems that the flagellum plays an underappreciated role in regulating gene expression. Roles of bacterial flagella in microbial processesThe bacterial flagellum is a complex rotary engine comprised of three basic parts: basal body, hook and filament [1] (Figure 1). The basal body anchors the flagellum in the cell envelope, and also contains the motor and a specialized type III secretion system (T3SS) for exporting flagellar proteins. The motor consists of a motile part, or rotor, that is connected to the hook via the rod, and a stationary part, or stator, which converts the potential energy of an electrochemical gradient to kinetic motion of the rotor. The hook is a flexible coupling that transfers torque from motor to the propeller-like filament In addition to motility, flagella have roles in other microbial processes, such as adherence to host cells, host cell invasion, protein secretion, autoagglutination (i.e. clumping or selfadherence of bacterial cells) and biofilm formation [2][3][4][5][6]. For some of these processes a direct involvement of flagella is clear. For example, Campylobacter jejuni flagella are responsible for secretion of several non-flagellar proteins [7][8][9]. Interestingly, some obligate intracellular symbionts of insects (e.g. Buchnera aphidicola) have lost many of the genes needed for assembly of the flagellum and appear to use the remaining flagellar assembly gene products for export of bacterial proteins to the host [10][11][12].For other processes, such as biofilm formation, it is difficult to ascertain the specific role of flagella, which can be quite different among bacteria. For example, flagella contribute to biofilm formation by acting as adhesins to promote attachment to surfaces in Aeromonas spp.[13], but not in Escherichia coli [14]. Additionally, studies with non-motile (Mot − ) mutants that make but are unable to rotate flagella, although useful, do not distinguish if a particular trait of a mutant is due to defects in locomotion, chemotaxis or just flagellar rotation (independently of the first two processes). Indeed, recent studies suggest a role for flagellar © 2009 Elsevier Ltd. All rights reserved.Corresponding author: Hoover, T.R. (trhoover@uga.edu). Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we ar...

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Helicobacter pylori extracellular proteins are of interest because of possible roles in pathogenesis, host recognition, and vaccine development. We utilized a unique approach by growing two strains (including one nonsequenced strain) in a defined serum-free medium and directly analyzing the proteins present in the culture supernatants by LC-MS/MS. Over 125 proteins were identified in the extracellular proteomes of two H. pylori strains. Forty-five of these proteins were enriched in the extracellular fraction when compared to soluble cell-associated protein samples. Our analysis confirmed and expanded on the previously reported H. pylori extracellular proteome. Extracellular proteins of interest identified here included cag pathogenicity island protein Cag24 (CagD); proteases HP0657 and HP1012; a polysaccharide deacetylase, HP0310, possibly involved in the hydrolysis of acetyl groups from host N-acetylglucosamine residues or from residues on the cell surface; and HP0953, an uncharacterized protein that appears to be restricted to Helicobacter species that colonize the gastric mucosa. In addition, our analysis found eight previously unidentified outer membrane proteins and two lipoproteins that could be important cell surface proteins.