| 1. |
- Drobni, Mirva, et al.
(författare)
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A host-derived pentapeptide affecting adhesion, proliferation and local pH in Streptococcus-Actinomyces biofilm communities.
- 2006
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Ingår i: Infection and immunity.
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Forskningsöversikt (populärvet., debatt m.m.)abstract
- Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordonii. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif, and selectively stimulated oral colonization of this organism in a rat model in vivo. By contrast, growth of Streptococcus mutans, implicated in caries, was unaffected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated pH-increase (i.e. ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PRP degradation and Arg catabolism, while cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 out of 10 strains) but not of S. gordonii (n=5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordonii to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacteria interaction where a host peptide released by bacterial proteolysis affects key properties in biofilm formation.
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| 2. |
- Herstad-Svärd, S., et al.
(författare)
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Ramprogram – Åtgärder för samtidig minimering av alkalirelaterade driftproblem, Etapp 2
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Combustion of an increasing amount of biofuel and waste woods has resulted in certainenvironmental advantages, including decreased emissions of fossil CO2, SO2 andmetals. On the other hand, a number of chloride and alkali related operational problemshave occurred which are related to combustion of these fuels.Alkali related operational problems have been studied in a project consisting of twoparts. The overall scope has been to characterise the operational problems and to studymeasures to minimise them. The first part was reported in Värmeforsk report 997 wherethe results were summarised in a table of different measures. In part two, additionalmeasures have been included in the test plan and initial corrosion has been studiedlinked to the different measures. The tests have also in part two been carried out at the12 MW CFB boiler at Chalmers. The effect of the selected measures has beeninvestigated concerning both deposit formation and bed agglomeration, and at the sametime emissions and other operational conditions were characterised.The second part of the project has among other things focused on:• To investigate measures which decrease the content of alkali and chloride in thedeposits, and consequently decrease the risk for corrosion (by investigating theinitial corrosion). Focus was also on trying to explain favourable effects.• To investigate if it is possible to combine a rather low dosage of kaolin and injectionof ammonium sulphate. This was done in order to reduce both bed agglomerationand problems from deposits during combustion of fuels rich in chlorine.• To investigate if co-combustion with sewage sludge, de-inking sludge or peat withhigh ash content, could give similar advantages as conventional additives.• Investigate if ash from PFBC is possible to use as an alternative bed material.By comparing the different measures in part two, it could be concluded that cocombustionof sewage sludge gave the best overall effect. The judgement was based onthe effects concerning bed agglomeration, level of alkali chloride in the flue gas,deposits and initial corrosion. Simultaneous addition of kaolin and ammonia sulphatealso had a favourable impact both in the bed and on the alkali chlorides in the gas phase.Dosage of kaolin did not reduce the effect of injected ammonium sulphate. Cocombustionof peat could also be a very attractive alternative, but it is critical to select asuitable peat type. It is of special concern to avoid peat with a high content of calcium,since it can increase the level of alkali chlorides by reacting with available sulphur.Change of bed material to ash from PFBC can decrease problems with bedagglomeration, but there is a risk of increased deposit formation and corrosion. A boileroperated with high steam data should consequently combine the change of bed materialwith injection of ammonium sulphate or another source of sulphur.Co-combustion of de-inking sludge from pulp and paper production can reduceproblems with bed agglomeration. There is, however, an increased chance of corrosiondue to the high content of calcium. Injection of sulphates may improve the situationconcerning corrosion. The results also showed that low potassium chlorine content in the flue gas decreasesthe risk of corrosion. Increased amount of potassium chlorine content in the flue gaswill not necessary give a high amount of chlorine content in the deposits if there is sulphur in the system.Key words: agglomeration, deposits, corrosion, alkali, kaolin, ammonium sulphate,sludge
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| 3. |
- Jakubovics, N.S., et al.
(författare)
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Interactions of mitis group streptococci with sialic acid receptors
- 2006
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Ingår i: International Congress Series 1289. - : Elsevier B.V.. ; , s. 275-278
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The serine-rich repeat glycoprotein Hsa in Streptococcus gordonii Challis mediates bacterial cell interactions with fetuin, glycocalicin, fibronectin and human platelets. Different strains of S.gordonii vary markedly in their adhesion levels to sialylated proteins, while other mitis group streptococci have distinct patterns of recognition of sialylated or desialylated receptor oligosaccharides. 2005 Elsevier B.V. All rights reserved.
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