Recently evolved combination of unique sulfatase and amidase genes enables bacterial degradation of the wastewater micropollutant acesulfame worldwide

Xenobiotics often challenge the principle of microbial infallibility. One example is acesulfame introduced in the 1980s as zero-calorie sweetener, which was recalcitrant in wastewater treatment plants until the early 2010s. Then, efficient removal has been reported with increasing frequency. By studying acesulfame metabolism in alphaproteobacterial degraders of the genera Bosea and Chelatococcus, we experimentally confirmed the previously postulated route of two subsequent hydrolysis steps via acetoacetamide-N-sulfonate (ANSA) to acetoacetate and sulfamate. Genome comparison of wildtype Bosea sp. 100-5 and an acesulfame degradation-defective mutant revealed the involvement of two plasmid-borne gene clusters. The acesulfame-hydrolyzing sulfatase is strictly manganese-dependent and belongs to the metallo beta-lactamase family. In all degraders analyzed, it is encoded on a highly conserved gene cluster embedded in a composite transposon. The ANSA amidase, on the other hand, is an amidase signature domain enzyme encoded in another gene cluster showing variable length among degrading strains. Transposition of the sulfatase gene cluster between chromosome and plasmid explains how the two catabolic gene clusters recently combined for the degradation of acesulfame. Searching available genomes and metagenomes for the two hydrolases and associated genes indicates that the acesulfame plasmid evolved and spread worldwide in short time. While the sulfatase is unprecedented and unique for acesulfame degraders, the amidase occurs in different genetic environments and likely evolved for the degradation of other substrates. Evolution of the acesulfame degradation pathway might have been supported by the presence of structurally related natural and anthropogenic compounds, such as aminoacyl sulfamate ribonucleotide or sulfonamide antibiotics.

Anti-cyclic citrullinated peptide revised criteria for the classification of rheumatoid arthritis

OBJECTIVE

The classification of rheumatoid arthritis (RA) is increasingly important as new therapies can halt the disease in its early stages. Antibodies to cyclic citrullinated peptides (anti-CCP) are widely used for RA diagnosis, but are not in the 1987 American College of Rheumatology (ACR) Criteria for RA Classification. We developed and tested the performance characteristics of new criteria for RA classification, incorporating anti-CCP.

METHODS

We identified all subjects seen in our arthritis centre with rheumatoid factor (RF) and anti-CCP tested simultaneously between 1 January and 30 June 2004 and reviewed their medical records for the ACR criteria, rheumatologists' diagnoses, RF and anti-CCP. We revised the ACR criteria in two ways: (a) adding anti-CCP, and (b) replacing rheumatoid nodules and erosions with anti-CCP (CCP 6 criteria). We compared sensitivity and specificity of all criteria, in all subjects and in subjects with arthritis symptoms </=6 months.

RESULTS

Medical records of 292 subjects were analysed: mean age was 54 years, 82% were women, and mean symptom duration was 4.1 years. 17% were RF positive and 14% were anti-CCP positive at initial testing. 78 (27%) had definite RA per treating rheumatologist at latest follow-up. The CCP 6 criteria increased sensitivity for RA classification for all subjects regardless of symptom duration: 74% vs 51% for ACR criteria with a loss in specificity (81% vs 91%). Sensitivity was greatly improved in subjects with symptoms < or =6 months: 25% vs 63% for ACR criteria with a decrease in specificity.

CONCLUSIONS

The CCP 6 criteria improved upon the sensitivity of the ACR criteria, most remarkably for subjects with symptoms < or =6 months and could be used for the classification of subjects for RA in clinical studies.