Pro-atherogenic lung and oral pathogens induce an inflammatory response in human and mouse mast cells

A broad variety of microbes are present in atherosclerotic plaques and chronic bacterial infection increases the risk of atherosclerosis by mechanisms that have remained vague. One possible mechanism is that bacteria or bacterial products activate plaque mast cells that are known to participate in the pathogenesis of atherosclerosis. Here, we show by real-time PCR analysis and ELISA that Chlamydia pneumoniae (Cpn) and a periodontal pathogen, Aggregatibacter actinomycetemcomitans (Aa), both induce a time and concentration-dependent expression and secretion of interleukin 8 (IL-8), tumour necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) by cultured human peripheral blood-derived mast cells, but not anti-inflammatory molecules, such as IL-10 or transforming growth factor β1 (TGF-β1). The IL-8 and MCP-1 responses were immediate, whereas the onset of TNF-α secretion was delayed. The Cpn-mediated pro-inflammatory effect was attenuated when the bacteria were inactivated by UV-treatment. Human monocyte-derived macrophages that were pre-infected with Cpn also induced a significant pro-inflammatory response in human mast cells, both in cocultures and when preconditioned media from Cpn-infected macrophages were used. Intranasal and intravenous administration of live Cpn and Aa, respectively induced an accumulation of activated mast cells in the aortic sinus of apolipoprotein E-deficient mice, however, with varying responses in the systemic levels of lipopolysaccharide (LPS) and TNF-α. Pro-atherogenic Cpn and Aa induce a pro-inflammatory response in cultured human connective tissue-type mast cells and activation of mouse aortic mast cells in vivo .     

Characterization of a New Epidemic Necrotic Pyoderma in Fur Animals and Its Association with Arcanobacterium phocae Infection

A new type of pyoderma was detected in Finnish fur animals in 2007. The disease continues to spread within and between farms, with severe and potentially fatal symptoms. It compromises animal welfare and causes considerable economic losses to farmers. A case-control study was performed in 2010–2011 to describe the entity and to identify the causative agent. Altogether 99 fur animals were necropsied followed by pathological and microbiological examination. The data indicated that the disease clinically manifests in mink (Neovison vison) by necrotic dermatitis of the feet and facial skin. In finnraccoons (Nyctereutes procyonoides), it causes painful abscesses in the paws. Foxes (Vulpes lagopus) are affected by severe conjunctivitis and the infection rapidly spreads to the eyelids and facial skin. A common finding at necropsy was necrotic pyoderma. Microbiological analysis revealed the presence of a number of potential causative agents, including a novel Streptococcus sp. The common finding from all diseased animals of all species was Arcanobacterium phocae. This bacterium has previously been isolated from marine mammals with skin lesions but this is the first report of A. phocae isolated in fur animals with pyoderma. The results obtained from this study implicate A. phocae as a potential causative pathogen of fur animal epidemic necrotic pyoderma (FENP) and support observations that the epidemic may have originated in a species -shift of the causative agent from marine mammals. The variable disease pattern and the presence of other infectious agents (in particular the novel Streptococcus sp.) suggest a multifactorial etiology for FENP, and further studies are needed to determine the environmental, immunological and infectious factors contributing to the disease.     

Systemic and mucosal antibody response in experimental Chlamydia pneumoniae infection of mice

Chlamydia pneumoniae is a common human respiratory pathogen, and sera from infected individuals recognize several proteins of C. pneumoniae. We produced C. pneumoniae-specific proteins in a Bacillus subtilis expression system. We then used these recombinant C. pneumoniae proteins and purified C. pneumoniae elementary bodies as antigens in enzyme immunoassays to assess the kinetics and protein specificity of the systemic and mucosal antibody responses induced by C. pneumoniae intranasal infection in BALB/c mice. The systemic antibodies in mice recognized strong 'key' immunogens of Chlamydia, Omp2 and Hsp60, but weakly targeted the MOMP protein, the major immunogen in chlamydial species other than C. pneumoniae. The IgA antibodies in bronchial secretions specifically recognized the putative surface protein of C. pneumoniae, Omp4. Our preliminary observations point to the necessity of further characterization of the mucosal antibody response during C. pneumoniae infection.     

Bacteria Contribute to Sediment Nutrient Release and Reflect Progressed Eutrophication-Driven Hypoxia in an Organic-Rich Continental Sea

In the sedimental organic matter of eutrophic continental seas, such as the largest dead zone in the world, the Baltic Sea, bacteria may directly participate in nutrient release by mineralizing organic matter or indirectly by altering the sediment’s ability to retain nutrients. Here, we present a case study of a hypoxic sea, which receives riverine nutrient loading and in which microbe-mediated vicious cycles of nutrients prevail. We showed that bacterial communities changed along the horizontal loading and vertical mineralization gradients in the Gulf of Finland of the Baltic Sea, using multivariate statistics of terminal restriction fragments and sediment chemical, spatial and other properties of the sampling sites. The change was mainly explained by concentrations of organic carbon, nitrogen and phosphorus, which showed strong positive correlation with Flavobacteria, Sphingobacteria, Alphaproteobacteria and Gammaproteobacteria. These bacteria predominated in the most organic-rich coastal surface sediments overlain by oxic bottom water, whereas sulphate-reducing bacteria, particularly the genus Desulfobacula, prevailed in the reduced organic-rich surface sediments in the open sea. They correlated positively with organic nitrogen and phosphorus, as well as manganese oxides. These relationships suggest that the bacterial groups participated in the aerobic and anaerobic degradation of organic matter and contributed to nutrient cycling. The high abundance of sulphate reducers in the surficial sediment layers reflects the persistence of eutrophication-induced hypoxia causing ecosystem-level changes in the Baltic Sea. The sulphate reducers began to decrease below depths of 20 cm, where members of the family Anaerolineaceae (phylum Chloroflexi) increased, possibly taking part in terminal mineralization processes. Our study provides valuable information on how organic loading affects sediment bacterial community compositions, which consequently may maintain active nutrient recycling. This information is needed to improve our understanding on nutrient cycling in shallow seas where the dead zones are continuously spreading worldwide.     

Biodegradation of pentachlorophenol in natural soil by inoculatedRhodococcus chlorophenolicus

Rhodococcus chlorophenolicus PCP-1, a mineralizer of polychlorinated phenols, was inoculated into natural sandy loam and peaty soils with pentachlorophenol (PCP) at concentrations usually found at lightly and heavily polluted industrial sites (30 to 600 mg PCP/kg). A single inoculum of 10⁵ to 10⁸ cells per g of peat soil and as little as 500 cells/g sandy soil initiated mineralization of¹⁴C-PCP. The mineralization rates of PCP were 130 to 250 mg mineralized per kg soil in 4 months in the heavily (600 mg/kg) polluted soils and 13 to 18 mg/kg in the lightly (30 mg/kg) polluted soils. There were no detectable PCP mineralizing organisms in the soils prior to inoculation, and also there was no significant adaptation of the indigenous microbial population to degrade PCP during 4 months observation in the uninoculated soils. The inoculum-induced mineralization continued for longer than 4 months after a single inoculation. Uninoculated, lightly polluted soils (30 mg PCP/kg) also showed loss of PCP, but some of this reappeared as pentachloroanisol and other organic chlorine compounds (EOX). Such products did not accumulate in theR. chlorophenolicus-inoculated soils, where instead EOX was mineralized 90 to 98%.R. chlorophenolicus mineralized PCP unhindered by the substrate competition offered by the PCP-methylating bacteria indigenously occurring in the soils or by simultaneously inoculated O-methylatingR. rhodochrous.     

O-Methylation of Chlorinated para-Hydroquinones by Rhodococcus chlorophenolicus

Rhodococcus chlorophenolicus PCP-I, a degrader of polychlorinated phenols, guaiacols (2-methoxyphenols), and syringols (2,6-dimethoxyphenols), was shown to O-methylate the degradation intermediate, a chlorinated para-hydroquinone, into 4-methoxyphenol. O-methylation was constitutively expressed, whereas the degradation of chlorophenols and chlorohydroquinones was inducible in R. chlorophenolicus. The O-methylating reaction required two hydroxyl groups in positions para to each other. R. chlorophenolicus selectively methylated the hydroxyl group flanked by two chlorine substituents. Tetrachlorohydroquinone, trichlorohydroquinone, and 2,6-dichlorohydroquinone were methylated into tetrachloro-4-methoxyphenol, 2,3,5-trichloro-4-methoxyphenol, and 3,5-dichloro-4-methoxyphenol, respectively. Chlorohydroquinones with only one chlorine adjacent to a hydroxyl group were methylated only in trace amounts, and no metabolite was formed from hydroquinone. The degradation intermediates formed in hydroxylation of tetrachloroguaiacol and trichlorosyringol by R. chlorophenolicus were O-methylated into two isomeric trichlorodimethoxyphenols and two isomeric dichlorotrimethoxyphenols, respectively. R. chlorophenolicus also degraded the polychlorinated methylation products (tetrachlorinated and trichlorinated 4-methoxyphenols), but not mono- and dichlorinated 4-methoxyphenols.     

Virulence of Agrobacterium tumefaciens requires phosphatidylcholine in the bacterial membrane

Phosphatidylcholine (PC, lecithin) has long been considered a solely eukaryotic membrane lipid. Only a minority of all bacteria is able to synthesize PC. The plant‐transforming bacterium Agrobacterium tumefaciens encodes two potential PC forming enzymes, a phospholipid N‐methyltransferase (PmtA) and a PC synthase (Pcs). We show that PC biosynthesis and tumour formation on Kalanchoë plants was impaired in the double mutant. The virulence defect was due to a complete lack of the type IV secretion machinery in the Agrobacterium PC mutant. Our results strongly suggest that PC in bacterial membranes is an important determinant for the establishment of host–microbe interactions.     

Detecting species-site dependencies in large multiple sequence alignments

Multiple sequence alignments (MSAs) are one of the most important sources of information in sequence analysis. Many methods have been proposed to detect, extract and visualize their most significant properties. To the same extent that site-specific methods like sequence logos successfully visualize site conservations and sequence-based methods like clustering approaches detect relationships between sequences, both types of methods fail at revealing informational elements of MSAs at the level of sequence–site interactions, i.e. finding clusters of sequences and sites responsible for their clustering, which together account for a high fraction of the overall information of the MSA. To fill this gap, we present here a method that combines the Fisher score-based embedding of sequences from a profile hidden Markov model (pHMM) with correspondence analysis. This method is capable of detecting and visualizing group-specific or conflicting signals in an MSA and allows for a detailed explorative investigation of alignments of any size tractable by pHMMs. Applications of our methods are exemplified on an alignment of the Neisseria surface antigen LP2086, where it is used to detect sites of recombinatory horizontal gene transfer and on the vitamin K epoxide reductase family to distinguish between evolutionary and functional signals.