Maaperän ja pohjaveden kunnostus - yleisimpien menetelmien esittely

Suomessa on noin 20 000 pilaantuneeksi epäiltyä maa-aluetta, joista useista aiheutuu myös pohjaveden pilaantumista. Jos pilaantuminen aiheuttaa riskin ihmisen terveydelle tai ympäristölle, tulee alue kunnostaa. Nykyisin erilaisia maaperän ja pohjaveden kunnostusmenetelmiä on tarjolla runsaasti. Niiden soveltuvuus vaihtelee kohteittain riippuen mm. pilaantumisen aiheuttaneesta haitta-aineesta, käsiteltävän alueen laajuudesta ja maaperän ominaisuuksista. Tässä julkaisussa esitellään yleisimpiä Suomessa käytössä olevia maaperän ja pohjaveden kunnostusmenetelmiä. Menetelmistä on esitetty niiden pääperiaate, soveltuvuus eri haitta-aineille ja maaperätyypeille, menetelmien tekniset rajoitukset, arvioidut käsittelykustannukset ja käsittelyn kesto. Lisäksi on kerrottu menetelmän käytöstä ja soveltuvuudesta Suomessa ja annettu viitteitä lisätietojen etsimistä varten. Yleisimpien menetelmien ohella on esitetty eräitä menetelmiä, jotka ovat käytössä muualla maailmassa, mutta voisivat soveltua myös Suomeen. Tämän julkaisu soveltuu käytettäväksi parhaiten silloin, kun tehdään alustavaa valintaa käyttökelpoisten menetelmien kesken. Lopullinen menetelmän valinta vaatii kohdekohtaisia selvityksiä pilaantuneella alueella

Gliding motility and expression of motility-related genes in spreading and nonspreading colonies of Flavobacterium columnare

Gliding motility machinery enables moving on surfaces in many species among Bacteroidetes, resulting in bacterial colonies with spreading appearance. The adhesins required for gliding are secreted through a gliding motility –associated protein secretion system known as the type IX secretion system (T9SS). The fish pathogen Flavobacterium columnare produces spreading (Rhizoid, Rz; Soft, S) and nonspreading (Rough, R) colony types, of which only the spreading Rz type is virulent. In this study, we explored the spreading behaviour of these colony types by microscopic imaging and measured the expression of genes associated with gliding motility and T9SS (gldG, gldH, gldL, sprA, sprB, sprE, sprF, sprT and porV) under high and low resource levels. The spreading colony types responded to low resource level by increased colony size. The nonspreading colony type as well as the cells subjected to high nutrient level expressed only moderate cell movements. Yet, low nutrient level provoked more active gliding motility by individual cells and increased biofilm spreading by cooperative gliding. The gene expression survey demonstrated an increased expression level of sprA and sprF under low nutrient conditions. Surprisingly, the expression of gliding motility genes was not consistently associated with more active spreading behaviour. Our study demonstrates that environmental nutrient level is an important regulator of gliding motility and also the expression of some of the associated genes. Furthermore, our results may help to understand the connections between nutrient concentration, gliding motility and virulence of F. columnare.peerReviewedpeerReviewe

Comparing the different morphotypes of a fish pathogen - implications for key virulence factors in Flavobacterium columnare

Background: Flavobacterium columnare (Bacteroidetes) is the causative agent of columnaris disease in farmed freshwater fish around the world. The bacterium forms three colony morphotypes (Rhizoid, Rough and Soft), but the differences of the morphotypes are poorly known. We studied the virulence of the morphotypes produced by F. columnare strain B067 in rainbow trout ( Onconrhynchus mykiss ) and used high-resolution scanning electron microscopy to identify the fine structures of the cells grown in liquid and on agar. We also analysed the proteins secreted extracellularly and in membrane vesicles to identify possible virulence factors. Results: Only the Rhizoid morphotype was virulent in rainbow trout. Under electron microscopy, the cells of Rhizoid and Soft morphotypes were observed to display an organised structure within the colony, whereas in the Rough type this internal organisation was absent. Planktonic cells of the Rhizoid and Rough morphotypes produced large membrane vesicles that were not seen on the cells of the Soft morphotype. The vesicles were purified and analysed. Two proteins with predicted functions were identified, OmpA and SprF. Furthermore, the Rhizoid morphotype secreted a notable amount of a small, unidentified 13 kDa protein absent in the Rough and Soft morphotypes, indicating an association with bacterial virulence. Conclusions: Our results suggest three factors that are associated with the virulence of F. columnare : the coordinated organisation of cells, a secreted protein and outer membrane vesicles. The internal organisation of the cells within a colony may be associated with bacterial gliding motility, which has been suggested to be connected with virulence in F. columnare . The function of the secreted 13 kDa protein by the cells of the virulent morphotype cells remains unknown. The membrane vesicles might be connected with the adhesion of cells to the surfaces and could also carry potential virulence factors. Indeed, OmpA is a virulence factor in several bacterial pathogens, often linked with adhesion and invasion, and SprF is a protein connected with gliding motility and the protein secretion of flavobacteria.peerReviewe

Data_Sheet_1.docx

<p>Gliding motility facilitates the movement of bacteria along surfaces in many Bacteroidetes species and results in spreading colonies. The adhesins required for the gliding are secreted through a gliding motility-associated protein secretion system, known as the type IX secretion system (T9SS). The fish pathogen Flavobacterium columnare produces spreading (rhizoid [Rz], soft [S]) and non-spreading (rough [R]) colony types, of which only the spreading Rz type is virulent. In this study, we explored the spreading behavior of these colony types by microscopic imaging and measured the expression of genes associated with gliding motility and T9SS (gldG, gldH, gldL, sprA, sprB, sprE, sprF, sprT, and porV) under high and low resource levels by using RT-qPCR (reverse transcription quantitative PCR). The spreading colony types responded to the low resource level with increased colony size. The non-spreading colony type, as well as the cells growing under high nutrient level expressed only moderate cell movements. Yet, a low nutrient level provoked more active gliding motility in individual cells and increased spreading by cooperative gliding. The gene expression survey demonstrated an increased expression level of sprA (a core component of T9SS) and sprF (needed for adhesin secretion) under low nutrient conditions. Surprisingly, the expression of gliding motility genes was not consistently associated with more active spreading behavior. Furthermore, no genetic differences were found between spreading and non-spreading colony types in the studied genes associated with gliding motility. Our study demonstrates that environmental nutrient level is an important regulator of both gliding motility and the expression of some of the associated genes. These results may help to understand the connections between nutrient concentration, gliding motility, and virulence of F. columnare.</p

High Nutrient Concentration Can Induce Virulence Factor Expression and Cause Higher Virulence in an Environmentally Transmitted Pathogen

Environmentally transmitted opportunistic pathogens shuttle between two substantially different environments: outside-host and within-host habitats. These environments differ from each other especially with respect to nutrient availability. Consequently, the pathogens are required to regulate their behavior in response to environmental cues in order to survive, but how nutrients control the virulence in opportunistic pathogens is still poorly understood. In this study, we examined how nutrient level in the outside-host environment affects the gene expression of putative virulence factors of the opportunistic fish pathogen Flavobacterium columnare. The impact of environmental nutrient concentration on bacterial virulence was explored by cultivating the bacteria in various nutrient conditions, measuring the gene expression of putative virulence factors with RT-qPCR and, finally, experimentally challenging rainbow trout (Oncorhynchus mykiss) fry with these bacteria. Our results show that increased environmental nutrient concentration can increase the expression of putative virulence genes, chondroitinase (cslA) and collagenase, in the outside-host environment and may lead to more rapid fish mortality. These findings address that the environmental nutrients may act as significant triggers of virulence gene expression and therefore contribute to the interaction between an environmentally transmitted opportunistic pathogen and its host.peerReviewe

Video_9.mp4

<p>Gliding motility facilitates the movement of bacteria along surfaces in many Bacteroidetes species and results in spreading colonies. The adhesins required for the gliding are secreted through a gliding motility-associated protein secretion system, known as the type IX secretion system (T9SS). The fish pathogen Flavobacterium columnare produces spreading (rhizoid [Rz], soft [S]) and non-spreading (rough [R]) colony types, of which only the spreading Rz type is virulent. In this study, we explored the spreading behavior of these colony types by microscopic imaging and measured the expression of genes associated with gliding motility and T9SS (gldG, gldH, gldL, sprA, sprB, sprE, sprF, sprT, and porV) under high and low resource levels by using RT-qPCR (reverse transcription quantitative PCR). The spreading colony types responded to the low resource level with increased colony size. The non-spreading colony type, as well as the cells growing under high nutrient level expressed only moderate cell movements. Yet, a low nutrient level provoked more active gliding motility in individual cells and increased spreading by cooperative gliding. The gene expression survey demonstrated an increased expression level of sprA (a core component of T9SS) and sprF (needed for adhesin secretion) under low nutrient conditions. Surprisingly, the expression of gliding motility genes was not consistently associated with more active spreading behavior. Furthermore, no genetic differences were found between spreading and non-spreading colony types in the studied genes associated with gliding motility. Our study demonstrates that environmental nutrient level is an important regulator of both gliding motility and the expression of some of the associated genes. These results may help to understand the connections between nutrient concentration, gliding motility, and virulence of F. columnare.</p

Video_5.mp4

<p>Gliding motility facilitates the movement of bacteria along surfaces in many Bacteroidetes species and results in spreading colonies. The adhesins required for the gliding are secreted through a gliding motility-associated protein secretion system, known as the type IX secretion system (T9SS). The fish pathogen Flavobacterium columnare produces spreading (rhizoid [Rz], soft [S]) and non-spreading (rough [R]) colony types, of which only the spreading Rz type is virulent. In this study, we explored the spreading behavior of these colony types by microscopic imaging and measured the expression of genes associated with gliding motility and T9SS (gldG, gldH, gldL, sprA, sprB, sprE, sprF, sprT, and porV) under high and low resource levels by using RT-qPCR (reverse transcription quantitative PCR). The spreading colony types responded to the low resource level with increased colony size. The non-spreading colony type, as well as the cells growing under high nutrient level expressed only moderate cell movements. Yet, a low nutrient level provoked more active gliding motility in individual cells and increased spreading by cooperative gliding. The gene expression survey demonstrated an increased expression level of sprA (a core component of T9SS) and sprF (needed for adhesin secretion) under low nutrient conditions. Surprisingly, the expression of gliding motility genes was not consistently associated with more active spreading behavior. Furthermore, no genetic differences were found between spreading and non-spreading colony types in the studied genes associated with gliding motility. Our study demonstrates that environmental nutrient level is an important regulator of both gliding motility and the expression of some of the associated genes. These results may help to understand the connections between nutrient concentration, gliding motility, and virulence of F. columnare.</p