Archaea, Bacteria, and methane production along environmental gradients in fens and bogs

Metanogeenit ovat hapettomissa oloissa eläviä arkkien pääryhmään kuuluvia mikrobeja, joiden ainutlaatuisen aineenvaihdunnan seurauksena syntyy metaania. Ilmakehässä metaani on voimakas kasvihuonekaasu. Yksi suurimmista luonnon metaanilähteistä ovat kosteikot. Pohjoisten soiden metaanipäästöt vaihtelevat voimakkaasti eri soiden välillä ja yhden suon sisälläkin, riippuen muun muassa vuodenajasta, suotyypistä ja kasvillisuudesta. Väitöskirjatyössä tutkittiin metaanipäästöjen vaihtelun mikrobiologista taustaa. Tutkimuksessa selvitettiin suotyypin, vuodenajan, tuhkalannoituksen ja turvesyvyyden vaikutusta metanogeeniyhteisöihin sekä metaanintuottoon kolmella suomalaisella suolla. Lisäksi tutkittiin ei-metanogeenisia arkkeja ja bakteereita, koska ne muodostavat metaanin tuoton lähtöaineet osana hapetonta hajotusta. Mikrobiyhteisöt analysoitiin DNA- ja RNA-lähtöisillä, polymeraasiketjureaktioon (PCR) perustuvilla menetelmillä. Merkkigeeneinä käytettiin metaanin tuottoon liittyvää mcrA-geeniä sekä arkkien ja bakteerien ribosomaalista 16S RNA-geeniä. Metanogeeniyhteisöt ja metaanintuotto erosivat huomattavasti happaman ja vähäravinteisen rahkasuon sekä ravinteikkaampien sarasoiden välillä. Rahkasuolta löytyi lähes yksinomaan Methanomicrobiales-lahkon metanogeeneja, jotka tuottavat metaania vedystä ja hiilidioksidista. Sarasoiden metanogeeniyhteisöt olivat monimuotoisempia, ja niillä esiintyi myös asetaattia käyttäviä metanogeeneja. Vuodenaika vaikutti merkittävästi metaanintuottoon. Talvella havaittiin odottamattoman suuri metaanintuottopotentiaali sekä viitteitä aktiivisista metanogeeneista. Arkkiyhteisön koostumus sen sijaan vaihteli vain vähän. Tuhkalannoitus, jonka tarkoituksena on edistää puiden kasvua ojitetuilla soilla, ei merkittävästi vaikuttanut metaanintuottoon tai -tuottajiin. Ojitetun suon yhteisöt kuitenkin muuttuivat turvesyvyyden mukaan. Vertailtaessa erilaisia PCR-menetelmiä todettiin, että kolmella mcrA-geeniin kohdistuvalla alukeparilla havaittiin pääosin samat ojitetun suon metanogeenit, mutta lajien runsaussuhteet riippuvat käytetyistä alukkeista. Soilla havaitut bakteerit kuuluivat pääjaksoihin Deltaproteobacteria, Acidobacteria ja Verrucomicrobia. Lisäksi löydettiin Crenarchaeota-pääjakson ryhmiin 1.1c ja 1.3 kuuluvia ei-metanogeenisia arkkeja. Tulokset ryhmien esiintymisestä hapettomassa turpeessa antavat lähtökohdan selvittää niiden mahdollisia vuorovaikutuksia metanogeenien kanssa. Tutkimuksen tulokset osoittivat, että metanogeeniyhteisön koostumus heijastaa metaanintuottoon vaikuttavia kemiallisia tai kasvillisuuden vaihteluita kuten suotyyppiä. Soiden metanogeenien ja niiden fysiologian parempi tuntemus voi auttaa ennustamaan ympäristömuutosten vaikutusta soiden metaanipäästöihin.

Surface Proteins of Lactobacillus crispatus: Adhesive Properties and Cell Wall Anchoring

Bacterial surface-associated proteins are important in communication with the environment and bacteria-host interactions. In this thesis work, surface molecules of Lactobacillus crispatus important in host interaction were studied. The L. crispatus strains of the study were known from previous studies to be efficient in adhesion to intestinal tract and ECM. L. crispatus JCM 5810 possess an adhesive surface layer (S-layer) protein, whose functions and domain structure was characterized. We cloned two S-layer protein genes (cbsA; collagen-binding S-layer protein A and silent cbsB) and identified the protein region in CbsA important for adhesion to host tissues, for polymerization into a periodic layer as well as for attachment to the bacterial cell surface. The analysis was done by extensive mutation analysis and by testing His6-tagged fusion proteins from recombinant Escherichia coli as well as by expressing truncated CbsA peptides on the surface of Lactobacillus casei. The N-terminal region (31-274) of CbsA showed efficient and specific binding to collagens, laminin and extracellular matrix on tissue sections of chicken intestine. The N-terminal region also contained the information for formation of periodic S-layer polymer. This region is bordered at both ends by a conserved short region rich in valines, whose substitution to leucines drastically affected the periodic polymer structure. The mutated CbsA proteins that failed to form a periodic polymer, did not bind collagens, which indicates that the polymerized structure of CbsA is needed for collagen-binding ability. The C-terminal region, which is highly identical in S-layer proteins of L. crispatus, Lactobacillus acidophilus and Lactobacillus helveticus, was shown to anchor the protein to the bacterial cell wall. The C-terminal CbsA peptide specifically bound to bacterial teichoic acid and lipoteichoic acids. In conclusion, the N-terminal domain of the S-layer protein of L. crispatus is important for polymerization and adhesion to host tissues, whereas the C-terminal domain anchors the protein to bacterial cell-wall teichoic acids. Lactobacilli are fermentative organisms that effectively lower the surrounding pH. While this study was in progress, plasminogen-binding proteins enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were identified in the extracellular proteome of L. crispatus ST1. In this work, the cell-wall association of enolase and GAPDH were shown to rely on pH-reversible binding to the cell-wall lipoteichoic acids. Enolase from L. crispatus was functionally compared with enolase from L. johnsonii as well as from pathogenic streptococci (Streptococcus pneumoniae, Streptococcus pyogenes) and Staphylococcus aureus. His6-enolases from commensal lactobacilli bound human plasminogen and enhanced its activation by human plasminogen activators similarly to, or even better than, the enolases from pathogens. Similarly, the His6-enolases from lactobacilli exhibited adhesive characteristics previously assigned to pathogens. The results call for more detailed analyses of the role of the host plasminogen system in bacterial pathogenesis and commensalism as well of the biological role and potential health risk of the extracellular proteome in lactobacilli.

Characterization of genomic diversity in extraintestinal pathogenic Escherichia coli (ExPEC) and development of a diagnostic DNA microarray for the differentiation of ExPEC isolates causing urinary tract infections

Extraintestinal pathogenic Escherichia coli (ExPEC) represent a diverse group of strains of E. coli, which infect extraintestinal sites, such as the urinary tract, the bloodstream, the meninges, the peritoneal cavity, and the lungs. Urinary tract infections (UTIs) caused by uropathogenic E. coli (UPEC), the major subgroup of ExPEC, are among the most prevalent microbial diseases world wide and a substantial burden for public health care systems. UTIs are responsible for serious morbidity and mortality in the elderly, in young children, and in immune-compromised and hospitalized patients. ExPEC strains are different, both from genetic and clinical perspectives, from commensal E. coli strains belonging to the normal intestinal flora and from intestinal pathogenic E. coli strains causing diarrhea. ExPEC strains are characterized by a broad range of alternate virulence factors, such as adhesins, toxins, and iron accumulation systems. Unlike diarrheagenic E. coli, whose distinctive virulence determinants evoke characteristic diarrheagenic symptoms and signs, ExPEC strains are exceedingly heterogeneous and are known to possess no specific virulence factors or a set of factors, which are obligatory for the infection of a certain extraintestinal site (e. g. the urinary tract). The ExPEC genomes are highly diverse mosaic structures in permanent flux. These strains have obtained a significant amount of DNA (predictably up to 25% of the genomes) through acquisition of foreign DNA from diverse related or non-related donor species by lateral transfer of mobile genetic elements, including pathogenicity islands (PAIs), plasmids, phages, transposons, and insertion elements. The ability of ExPEC strains to cause disease is mainly derived from this horizontally acquired gene pool; the extragenous DNA facilitates rapid adaptation of the pathogen to changing conditions and hence the extent of the spectrum of sites that can be infected. However, neither the amount of unique DNA in different ExPEC strains (or UPEC strains) nor the mechanisms lying behind the observed genomic mobility are known. Due to this extreme heterogeneity of the UPEC and ExPEC populations in general, the routine surveillance of ExPEC is exceedingly difficult. In this project, we presented a novel virulence gene algorithm (VGA) for the estimation of the extraintestinal virulence potential (VP, pathogenicity risk) of clinically relevant ExPECs and fecal E. coli isolates. The VGA was based on a DNA microarray specific for the ExPEC phenotype (ExPEC pathoarray). This array contained 77 DNA probes homologous with known (e.g. adhesion factors, iron accumulation systems, and toxins) and putative (e.g. genes predictably involved in adhesion, iron uptake, or in metabolic functions) ExPEC virulence determinants. In total, 25 of DNA probes homologous with known virulence factors and 36 of DNA probes representing putative extraintestinal virulence determinants were found at significantly higher frequency in virulent ExPEC isolates than in commensal E. coli strains. We showed that the ExPEC pathoarray and the VGA could be readily used for the differentiation of highly virulent ExPECs both from less virulent ExPEC clones and from commensal E. coli strains as well. Implementing the VGA in a group of unknown ExPECs (n=53) and fecal E. coli isolates (n=37), 83% of strains were correctly identified as extraintestinal virulent or commensal E. coli. Conversely, 15% of clinical ExPECs and 19% of fecal E. coli strains failed to raster into their respective pathogenic and non-pathogenic groups. Clinical data and virulence gene profiles of these strains warranted the estimated VPs; UPEC strains with atypically low risk-ratios were largely isolated from patients with certain medical history, including diabetes mellitus or catheterization, or from elderly patients. In addition, fecal E. coli strains with VPs characteristic for ExPEC were shown to represent the diagnostically important fraction of resident strains of the gut flora with a high potential of causing extraintestinal infections. Interestingly, a large fraction of DNA probes associated with the ExPEC phenotype corresponded to novel DNA sequences without any known function in UTIs and thus represented new genetic markers for the extraintestinal virulence. These DNA probes included unknown DNA sequences originating from the genomic subtractions of four clinical ExPEC isolates as well as from five novel cosmid sequences identified in the UPEC strains HE300 and JS299. The characterized cosmid sequences (pJS332, pJS448, pJS666, pJS700, and pJS706) revealed complex modular DNA structures with known and unknown DNA fragments arranged in a puzzle-like manner and integrated into the common E. coli genomic backbone. Furthermore, cosmid pJS332 of the UPEC strain HE300, which carried a chromosomal virulence gene cluster (iroBCDEN) encoding the salmochelin siderophore system, was shown to be part of a transmissible plasmid of Salmonella enterica. Taken together, the results of this project pointed towards the assumptions that first, (i) homologous recombination, even within coding genes, contributes to the observed mosaicism of ExPEC genomes and secondly, (ii) besides en block transfer of large DNA regions (e.g. chromosomal PAIs) also rearrangements of small DNA modules provide a means of genomic plasticity. The data presented in this project supplemented previous whole genome sequencing projects of E. coli and indicated that each E. coli genome displays a unique assemblage of individual mosaic structures, which enable these strains to successfully colonize and infect different anatomical sites.

Plasmids and aromatic degradation in Sphingomonas for bioremediation : Aromatic ring cleavage genes in soil and rhizosphere

Microbial degradation pathways play a key role in the detoxification and the mineralization of polyaromatic hydrocarbons (PAHs), which are widespread pollutants in soil and constituents of petroleum hydrocarbons. In microbiology the aromatic degradation pathways are traditionally studied from single bacterial strains with capacity to degrade certain pollutant. In soil the degradation of aromatics is performed by a diverse community of micro-organisms. The aim of this thesis was to study biodegradation on different levels starting from a versatile aromatic degrader Sphingobium sp. HV3 and its megaplasmid, extending to revelation of diversity of key catabolic enzymes in the environment and finally studying birch rhizoremediation in PAH-polluted soil. To understand biodegradation of aromatics on bacterial species level, the aromatic degradation capacity of Sphingobium sp. HV3 and the role of the plasmid pSKY4, was studied. Toluene, m-xylene, biphenyl, fluorene, phenanthrene were detected as carbon and energy sources of the HV3 strain. Tn5 transposon mutagenesis linked the degradation capacity of toluene, m-xylene, biphenyl and naphthalene to the pSKY4 plasmid and qPCR expression analysis showed that plasmid extradiol dioxygenases genes (bphC and xylE) are inducted by phenanthrene, m-xylene and biphenyl whereas the 2,4-dichlorophenoxyacetic acid herbicide induced the chlorocatechol 1,2-dioxygenase gene (tfdC) from the ortho-pathway. A method to study upper meta-pathway extradiol dioxygenase gene diversity in soil was developed. The extradiol dioxygenases catalyse cleavage of the aromatic ring between a hydroxylated carbon and an adjacent non-hydroxylated carbon (meta-cleavage). A high diversity of extradiol dioxygenases were detected from polluted soils. The detected extradiol dioxygenases showed sequence similarity to known catabolic genes of Alpha-, Beta-, and Gammaproteobacteria. Five groups of extradiol dioxygenases contained sequences with no close homologues in the database, representing novel genes. In rhizoremediation experiment with birch (Betula pendula) treatment specific changes of extradiol dioxygenase communities were shown. PAH pollution changed the bulk soil extradiol dioxygenase community structure and birch rhizosphere contained a more diverse extradiol dioxygenase community than the bulk soil showing a rhizosphere effect. The degradation of pyrene in soil was enhanced with birch seedlings compared to soil without birch. The complete 280,923 kb nucleotide sequence of pSKY4 plasmid was determined. The open reading frames of pSKY4 were divided into putative conjugative transfer, aromatic degradation, replication/maintaining and transposition/integration function-encoding proteins. Aromatic degradation orfs shared high similarity to corresponding genes in pNL1, a plasmid from the deep subsurface strain Novosphingobium aromaticivorans F199. The plasmid backbones were considerably more divergent with lower similarity, which suggests that the aromatic pathway has functioned as a plasmid independent mobile genetic element. The functional diversity of microbial communities in soil is still largely unknown. Several novel clusters of extradiol dioxygenases representing catabolic bacteria, whose function, biodegradation pathways and phylogenetic position is not known were amplified with single primer pair from polluted soils. These extradiol dioxygenase communities were shown to change upon PAH pollution, which indicates that their hosts function in PAH biodegradation in soil. Although the degradation pathways of specific bacterial species are substantially better depicted than pathways in situ, the evolution of degradation pathways for the xenobiotic compounds is largely unknown. The pSKY4 plasmid contains aromatic degradation genes in putative mobile genetic element causing flexibility/instability to the pathway. The localisation of the aromatic biodegradation pathway in mobile genetic elements suggests that gene transfer and rearrangements are a competetive advantage for Sphingomonas bacteria in the environment.

Expression, Enzymatic Activities and Subcellular Localization of Hepatitis E Virus and Semliki Forest Virus Replicase Proteins

Viruses are submicroscopic, infectious agents that are obligate intracellular parasites. They adopt various types of strategies for their parasitic replication and proliferation in infected cells. The nucleic acid genome of a virus contains information that redirects molecular machinery of the cell to the replication and production of new virions. Viruses that replicate in the cytoplasm and are unable to use the nuclear transcription machinery of the host cell have developed their own transcription and capping systems. This thesis describes replication strategies of two distantly related viruses, hepatitis E virus (HEV) and Semliki Forest virus (SFV), which belong to the alphavirus-like superfamily of positive-strand RNA viruses. We have demonstrated that HEV and SFV share a unique cap formation pathway specific for alphavirus-like superfamily. The capping enzyme first acts as a methyltransferase, catalyzing the transfer of a methyl group from S-adenosylmethionine to GTP to yield m7GTP. It then transfers the methylated guanosine to the end of viral mRNA. Both reactions are virus-specific and differ from those described for the host cell. Therefore, these capping reactions offer attractive targets for the development of antiviral drugs. Additionally, it has been shown that replication of SFV and HEV takes place in association with cellular membranes. The origin of these membranes and the intracellular localization of the components of the replication complex were studied by modern microscopy techniques. It was demonstrated that SFV replicates in cytoplasmic membranes that are derived from endosomes and lysosomes. According to our studies, site for HEV replication seems to be the intermediate compartment which mediates the traffic between endoplasmic reticulum and the Golgi complex. As a result of this work, a unique mechanism of cap formation for hepatitis E virus replicase has been characterized. It represents a novel target for the development of specific inhibitors against viral replication.

CMV-, EBV-, and HHV-6-DNAemia after liver transplantation

Viral infections caused by herpesviruses are common complications after organ transplantation and they are associated with substantial morbidity and even mortality. Herpesviruses remain in a latent state in a host after primary infection and may reactivate later. CMV infection is the most important viral infection after liver transplantation. Less is known about the significance of human herpesvirus-6 (HHV-6). EBV is believed to play a major role in the development of post-transplant lymphoproliferative disorders (PTLD). The aim of this study was to investigate the CMV-, EBV- and HHV-6 DNAemia after liver transplantation by frequent monitoring of adult liver transplant patients. The presence of CMV, EBV and HHV-6 DNA were demonstrated by in situ hybridization assays and by real-time PCR methods from peripheral blood specimens. CMV and HHV-6 antigens were demonstrated by antigenemia assays and compared to the viral DNAemia. The response to antiviral therapy was also investigated. CMV-DNAemia appeared earlier than CMV pp65-antigenemia after liver transplantation. CMV infections were treated with ganciclovir. However, most of the treated patients demonstrated persistence of CMV-DNA for up to several months. Continuous CMV-DNA expression of peripheral blood leukocytes showed that the virus is not eliminated by ganciclovir and recurrences can be expected during several months after liver transplantation. HHV-6 DNAemia / antigenemia was common and occurred usually within the first three months after liver transplantation together with CMV. The HHV-6 DNA expression in peripheral blood mononuclear cells correlated well with HHV-6 antigenemia. Antiviral treatment significantly decreased the number of HHV-6 DNA positive cells, demonstrating the response to ganciclovir treatment. Clinically silent EBV reactivations with low viral loads were relatively common after liver transplantation. These EBV-DNAemias usually appeared within the first three months after liver transplantation together with betaherpesviruses (CMV, HHV-6, HHV-7). One patient developed high EBV viral loads and developed PTLD. These results indicate that frequent monitoring of EBV-DNA levels can be useful to detect liver transplant patients at risk of developing PTLD.

Health-Related Quality of Life, Costs and Treatment of Inflammatory Rheumatic Diseases in Routine Practice : With special emphasis on biological drugs

Rheumatoid arthritis (RA) and other chronic inflammatory joint diseases already begin to affect patients health-related quality of life (HRQoL) in the earliest phases of these diseases. In treatment of inflammatory joint diseases, the last two decades have seen new strategies and treatment options introduced. Treatment is started at an earlier phase; combinations of disease-modifying anti-rheumatic drugs (DMARDs) and corticosteroids are used; and in refractory cases new drugs such as tumour necrosis factor (TNF) inhibitors or other biologicals can be started. In patients with new referrals to the Department of Rheumatology of the Helsinki University Central Hospital, we evaluated the 15D and the Stanford Health Assessment Questionnaire (HAQ) results at baseline and approximately 8 months after their first visit. Altogether the analysis included 295 patients with various rheumatic diseases. The mean baseline 15D score (0.822, SD 0.114) was significantly lower than for the age-matched general population (0.903, SD 0.098). Patients with osteoarthritis (OA) and spondyloarthropathies (SPA) reported the poorest HRQoL. In patients with RA and reactive arthritis (ReA) the HRQoL improved in a statistically significant manner during the 8-month follow-up. In addition, a clinically important change appeared in patients with systemic rheumatic diseases. HAQ score improved significantly in patients with RA, arthralgia and fibromyalgia, and ReA. In a study of 97 RA patients treated either with etanercept or adalimumab, we assessed their HRQoL with the RAND 36-Item Health Survey 1.0 (RAND-36) questionnaire. We also analysed changes in clinical parameters and the HAQ. With etanercept and adalimumab, the values of all domains in the RAND-36 questionnaire increased during the first 3 months. The efficacy of each in improving HRQoL was statistically significant, and the drug effects were comparable. Compared to Finnish age- and sex-matched general population values, the HRQoL of the RA patients was significantly lower at baseline and, despite the improvement, remained lower also at follow-up. Our RA patients had long-standing and severe disease that can explain the low HRQoL also at follow-up. In a pharmacoeconomic study of patients treated with infliximab we evaluated medical and work disability costs for patients with chronic inflammatory joint disease during one year before and one year after institution of infliximab treatment. Clinical and economic data for 96 patients with different arthritis diagnoses showed, in all patients, significantly improved clinical and laboratory variables. However, the medical costs increased significantly during the second period by 12 015 (95% confidence interval, 6 496 to 18 076). Only a minimal decrease in work disability costs occurred mean decrease 130 (-1 268 to 1 072). In a study involving a switch from infliximab to etanercept, we investigated the clinical outcome in 49 patients with RA. Reasons for switching were in 42% failure to respond by American College of Rheumatology (ACR) 50% criteria; in 12% adverse event; and in 46% non-medical reasons although the patients had responded to infliximab. The Disease Activity Score with 28 joints examined (DAS28) allowed us to measure patients disease activity and compare outcome between groups based on the reason for switching. In the patients in whom infliximab was switched to etanercept for nonmedical reasons, etanercept continued to suppress disease activity effectively, and 1-year drug survival for etanercept was 77% (95% CI, 62 to 97). In patients in the infliximab failure and adverse event groups, DAS28 values improved significantly during etanercept therapy. However, the 1-year drug survival of etanercept was only 43% (95% CI, 26 to 70) and 50% (95% CI, 33 to 100), respectively. Although the HRQoL of patients with inflammatory joint diseases is significantly lower than that of the general population, use of early and aggressive treatment strategies including TNF-inhibitors can improve patients HRQoL effectively. Further research is needed in finding new treatment strategies for those patients who fail to respond or lose their response to TNF-inhibitors.

Quantity and tone in Finnish lexically stressed syllables

This paper presents results from a study on the tonal aspects of quantity in Finnish lexically stressed syllables. Fourteen speakers produced a set of 66 utterances where the quantity and structure of the lexically stressed syllable was system- atically varied. The tonal aspects of the syllable nucleus and nucleus and coda in case of closed syllables was stud- ied in the framework of the Target Approximation theory as formulated by Yi Xu. The results show a clear tendency to- wards the quantity distinction and bimoracity in general in Finnish to be signalled tonally by a dynamic falling tone as opposed to a static high tone in short (one mora) nuclei.

Health-related quality of life, symptoms and comorbidity in inflammatory bowel disease

Health-related quality of life (HRQoL) measurement has become an important outcome in treatment trials and in health policy decisions. HRQoL can be measured by using generic or disease-specific tools. Generic instruments can be used for comparing health status among patients in different health states and conditions but they do not focus specifically on the issues relevant in a particular disease. Disease-specific tools may be more responsive to changes within a specific condition. In earlier studies, impairment of HRQoL has been evident in patients with inflammatory bowel disease (IBD), especially when the disease is active. Data about the impact of comorbidity or demographic characteristics of the patients on HRQoL are partly controversial. This study, which comprised 2913 adult IBD patients, examined HRQoL using the disease-specific IBDQ and the general 15D instruments. The 15D scores of IBD patients were compared with scores of a gender and age matched general population sample. Frequency of IBD symptoms and arrangement of therapy were studied and compared with those of IBD patients in an earlier European study. Furthermore, data of other chronic diseases of the patients were obtained from the Social Insurance Institution s reimbursement register and comorbidity of IBD patients was compared with that of age and gender matched controls. --- Of the respondents, 37% reported that they suffered from disturbing IBD symptoms weekly. In 17% of the patients, the symptoms greatly affected the ability to enjoy leisure activities, and 14% stated that these symptoms greatly affected their capacity to work. Despite that, the great majority (93%) of patients expressed satisfaction with their current treatment, which exceeded the rate observed in the other European patients. The mean IBDQ score was 163, as the possible range is 32-224, and disease activity was strongly correlated with HRQoL. Older age, comorbid diseases, and female gender were also related to impairment of HRQoL. Lower HRQoL scores were seen also in newly-diagnosed patients and in those with a history of surgery, especially after stoma or ileal pouch-anal anastomosis (IPAA) operation. The range of 15D scores was 0.30-1.00, with mean of 0.87. As with the IBDQ, disease activity, older age and history of surgery were correlated with the score. Both the newly-diagnosed patients and patients with a long-lasting disease had lower scores than average even after adjusting for age. The 15D scores of IBD patients were significantly lower than those of the control group. A strong correlation was seen between the 15D and the IBDQ scores. Comorbidity with other chronic diseases was observed in 29% of IBD patients. Connective tissue diseases, chronic obstructive pulmonary diseases, pernicious anaemia, and coronary heart disease (CHD) were significantly increased in patients with IBD. Especially female IBD patients appeared to be at increased risk for CHD, and patients who reported weekly IBD symptoms had a higher risk for having other chronic diseases in addition to IBD. Comorbidity impaired HRQoL, as measured with both generic and disease-specific tools. In conclusion, HRQoL is impaired in IBD patients. An understanding of predictors of HRQoL will help to recognise patients who will need special support.