Bacterially mediated precipitation in marine stromatolites

Stromatolites are laminated, lithified (CaCO₃) sedimentary deposits formed by precipitation and/or sediment accretion by cyanobacterial–bacterial mat communities. Stromatolites have been associated with these communities as far back as the Precambrian era some 2+ billion years ago. The means by which microbial communities mediate the precipitation processes have remained unclear, and are the subject of considerable debate and speculation. Two alternative explanations for microbially mediated precipitation include: (i) cyanobacterial photosynthesis increases pH in a system supersaturated in respect of CaCO₃, resulting in CaCO₃ precipitation and then laminated lithification, and (ii) decomposition of cyanobacterial extracellular organic matter (e.g. sheaths, mucilage and organic acids) by microheterotrophs leads to release of organic-bound Ca²⁺ ions and CaCO₃ precipitation. We evaluated these explanations by examining metabolically active, lithifying stromatolitic mat communities from Highborne Cay, Bahamas, using microautoradiography. Microautoradiographic detection of ¹⁴CO₂ fixation and ³H organic matter ( d -glucose and an amino acid mixture) utilization by photosynthetically active cyanobacteria and microheterotrophs, combined with community-level uptake experiments, indicate that bacteria, rather than cyanobacteria are the dominant sites of CaCO₃ deposition. In the oligotrophic waters in which stromatolites exist, microheterotrophs are reliant on the photosynthetic community as a main source of organic matter. Therefore, autotrophic production indirectly controls microbially mediated precipitation and stromatolite formation in these shallow marine environments.     

Bacterially Produced Recombinant Influenza Vaccines Based on Virus-Like Particles

Although current influenza vaccines are effective in general, there is an urgent need for the development of new technologies to improve vaccine production timelines, capacities and immunogenicity. Herein, we describe the development of an influenza vaccine technology which enables recombinant production of highly efficient influenza vaccines in bacterial expression systems. The globular head domain of influenza hemagglutinin, comprising most of the protein''s neutralizing epitopes, was expressed in E. coli and covalently conjugated to bacteriophage-derived virus-like particles produced independently in E.coli. Conjugate influenza vaccines produced this way were used to immunize mice and found to elicit immune sera with high antibody titers specific for the native influenza hemagglutinin protein and high hemagglutination-inhibition titers. Moreover vaccination with these vaccines induced full protection against lethal challenges with homologous and highly drifted influenza strains.     

Bacterially associated corrosion of aluminum surface in the air

Summary In a process of precision machining, corrosion of the surface of a precisely cut aluminum piece caused by bacteria was observed. A bacterium, Alcaligenes denitrificans, accumulated aluminum within the cell in granular form.     

Human Mucosal Associated Invariant T Cells Detect Bacterially Infected Cells

Control of infection with Mycobacterium tuberculosis (Mtb) requires Th1-type immunity, of which CD8⁺ T cells play a unique role. High frequency Mtb-reactive CD8⁺ T cells are present in both Mtb-infected and uninfected humans. We show by limiting dilution analysis that nonclassically restricted CD8⁺ T cells are universally present, but predominate in Mtb-uninfected individuals. Interestingly, these Mtb-reactive cells expressed the Vα7.2 T-cell receptor (TCR), were restricted by the nonclassical MHC (HLA-Ib) molecule MR1, and were activated in a transporter associated with antigen processing and presentation (TAP) independent manner. These properties are all characteristics of mucosal associated invariant T cells (MAIT), an “innate” T-cell population of previously unknown function. These MAIT cells also detect cells infected with other bacteria. Direct ex vivo analysis demonstrates that Mtb-reactive MAIT cells are decreased in peripheral blood mononuclear cells (PBMCs) from individuals with active tuberculosis, are enriched in human lung, and respond to Mtb-infected MR1-expressing lung epithelial cells. Overall, these findings suggest a generalized role for MAIT cells in the detection of bacterially infected cells, and potentially in the control of bacterial infection.     

Bacterially synthesized vertebrate calmodulin is a specific substrate for ubiquitination

Calmodulin purified from bacteria which express a cloned chicken calmodulin gene can be selectively conjugated with ubiquitin, using enzymes present in reticulocyte extracts. Analyses of peptide products generated from limited proteolytic digestion of the calmodulin conjugate containing a single ubiquitin indicate that lysine 115 on calmodulin is the site of linkage. This linkage site is identical to that previously reported for calmodulin purified from Dictyostelium discoideum. Substrate-dependent ATP hydrolysis by a partially purified ubiquitin conjugation enzyme system from reticulocyte extracts was used to determine the enzyme affinity to calmodulin. Km values of 7 and 9 microM were determined for dictyostelium and the bacterially expressed calmodulin, respectively. The bacterially expressed calmodulin, unlike the Dictyostelium protein, can also form conjugates containing a 2-5 molar ratio of ubiquitin but at a slower rate than that observed for conjugation at lysine 115. Results from these studies further support our hypothesis that the post-translational methylation of lysine 115 found in most forms of calmodulin serves the important function of protecting calmodulin from ubiquitination and from degradation by the cytoplasmic ubiquitin-dependent proteolytic pathway. The capability of the bacterially expressed calmodulin to form conjugates with a high molar ratio of ubiquitin suggests that the post-translational acetylation of the N terminus of calmodulin may serve a similar function.     

Bacterially Induced Weathering of Ultramafic Rock and Its Implications for Phytoextraction

The bioavailability of metals in soil is often cited as a limiting factor of phytoextraction (or phytomining). Bacterial metabolites, such as organic acids, siderophores, or biosurfactants, have been shown to mobilize metals, and their use to improve metal extraction has been proposed. In this study, the weathering capacities of, and Ni mobilization by, bacterial strains were evaluated. Minimal medium containing ground ultramafic rock was inoculated with either of two Arthrobacter strains: LA44 (indole acetic acid [IAA] producer) or SBA82 (siderophore producer, PO₄ solubilizer, and IAA producer). Trace elements and organic compounds were determined in aliquots taken at different time intervals after inoculation. Trace metal fractionation was carried out on the remaining rock at the end of the experiment. The results suggest that the strains act upon different mineral phases. LA44 is a more efficient Ni mobilizer, apparently solubilizing Ni associated with Mn oxides, and this appeared to be related to oxalate production. SBA82 also leads to release of Ni and Mn, albeit to a much lower extent. In this case, the concurrent mobilization of Fe and Si indicates preferential weathering of Fe oxides and serpentine minerals, possibly related to the siderophore production capacity of the strain. The same bacterial strains were tested in a soil-plant system: the Ni hyperaccumulator Alyssum serpyllifolium subsp. malacitanum was grown in ultramafic soil in a rhizobox system and inoculated with each bacterial strain. At harvest, biomass production and shoot Ni concentrations were higher in plants from inoculated pots than from noninoculated pots. Ni yield was significantly enhanced in plants inoculated with LA44. These results suggest that Ni-mobilizing inoculants could be useful for improving Ni uptake by hyperaccumulator plants.     

Pathway evolution,structurally speaking

Small-molecule metabolism forms the core of the metabolic processes of all living organisms. As early as 1945, possible mechanisms for the evolution of such a complex metabolic system were considered. The problem is to explain the appearance and development of a highly regulated complex network of interacting proteins and substrates from a limited structural and functional repertoire. By permitting the co-analysis of phylogeny and metabolism, the combined exploitation of pathway and structural databases, as well as the use of multiple-sequence alignment search algorithms, sheds light on this problem. Much of the current research suggests a chemistry-driven 'patchwork' model of pathway evolution, but other mechanisms may play a role. In the future, as metabolic structure and sequence space are further explored, it should become easier to trace the finer details of pathway development and understand how complexity has evolved.     

Bacterially contaminated oil mists in engineering works: a possible respiratory hazard

Oil-in-water emulsion cutting fluids are used extensively in the engineering industry and may become contaminated by large numbers of microorganisms from dust, debris, and from the workers' skin. During use, the emulsions are recycled from sumps below the machinery, and may be used for long periods of time before sumps are emptied. Aerosols of these emulsions containing all the components of the oil, including contaminating bacteria, are generated at the moving parts of the machinery. When operating machinery, workers may inhale large numbers of these micro-organisms. Bacteria isolated from the emulsions and from air sampled around machinery were mostly Gram-negative, and were predominantly Pseudomonas species. Inhalation of Gram-negative bacteria may potentially cause respiratory allergy or infection, or may lead to long-term deterioration in lung function in otherwise asymptomatic individuals. Preliminary tests have shown an immunological response, in a worker with work-related respiratory symptoms, to extracts of three Pseudomonas species isolated from emulsion.     

Bacterially enriched diet improves sexual performance of sterile male Mediterranean fruit flies

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), (medfly) is a polyphagous and cosmopolitan agricultural pest, targeted in many areas for control by the Sterile Insect Technique (SIT). Our objective in the present study was to test the hypothesis that a bacterially enriched diet provided to sterile males will improve their sexual performance in competitive settings that emulate natural conditions. Specifically we determined how feeding on diets enriched with Klebsiella oxytoca affected the ability of sterile males to compete for wild females against wild males, their ability to inhibit female receptivity, and their survival. We found that enriching the sterile male diet with K.oxytoca significantly improved mating competitiveness in the laboratory and in field cages. In addition, bacterially enriched sterile males inhibited female receptivity more efficiently than sugar fed males and survived longer duration of starvation. We conclude that inoculating mass reared sterile flies with bacteria prior to their release is a valid approach to improve the efficacy of SIT.     

Morphoanalysis of Bacterially Precipitated Subaqueous Calcium Carbonate from Weebubbie Cave,Australia

In this article, we present a previously unreported morphology of bacterially precipitated calcite (determined using XRD, FTIR, and SAED) occurring subaqueously in Weebubbie Cave. Observations using FESEM and TEM revealed spindle-shaped crystals with curved [hk.0] faces lying parallel to the c-axis. Calcite precipitated under conditions designed to mimic the inorganic solution chemistry of the cave revealed a different morphology. These differences between the crystals suggest that the formation of the cave crystals is a consequence of biologically activity.     

MAIT Cell Recognition of MR1 on Bacterially Infected and Uninfected Cells

Mucosal-associated invariant T cells are a unique population of T cells that express a semi-invariant αβ TCR and are restricted by the MHC class I-related molecule MR1. MAIT cells recognize uncharacterized ligand(s) presented by MR1 through the cognate interaction between their TCR and MR1. To understand how the MAIT TCR recognizes MR1 at the surface of APCs cultured both with and without bacteria, we undertook extensive mutational analysis of both the MAIT TCR and MR1 molecule. We found differential contribution of particular amino acids to the MAIT TCR-MR1 interaction based upon the presence of bacteria, supporting the hypothesis that the structure of the MR1 molecules with the microbial-derived ligand(s) differs from the one with the endogenous ligand(s). Furthermore, we demonstrate that microbial-derived ligand(s) is resistant to proteinase K digestion and does not extract with common lipids, suggesting an unexpected class of antigen(s) might be recognized by this unique lymphocyte population.