To find a biomarker for denitrification in activated sludge, five denitrifying strains isolated from three wastewater treatment plants were studied. These strains were selected from among 1,500 isolates for their excellent denitrifying properties. They denitrify quickly and have no lag phase when switching from aerobic to anoxic conditions. All strains have the cd1-type of nitrite reductase. The strains are Gram-negative rods and they all grow as filamentous chains when cultivated in liquid solution. The strains differ in colony morphology when grown on nutrient agar. Almost full-length 16S rDNA sequences were determined and phylogenetic analysis revealed that these strains are positioned among members of the genus Comamonas in the beta-subclass of the Proteobacteria. Signature nucleotides and bootstrap percentages were also analysed to verify this position. Strains 110, 123T, 2.99g, 5.38g and P17 were < or = 96.7% similar to known strains, but > or = 99.7% similar to each other, as judged from their 16S rDNA sequences, and grouped tightly together in the phylogenetic tree. Sequence motifs in the 16S rRNA gene were also found, suggesting the monophyletic origin of these strains. Nevertheless, some strains differed from the others, for example strain 110 branches early from the other strains and 5.38g is phenotypically more inert. Therefore, it is proposed that strains 110, 123T, 2.99g and P17 are classified into a new species, Comamonas denitrificans sp. nov., while the taxonomic status of strain 5.38g will have to await the outcome of further studies. The type strain of Comamonas denitrificans is 123T (ATCC 700936T).

Teachers’ teaching practice plays a key role in the learning process of pupils, and for teaching to be successful, teachers must have knowledge in many different fields. This obviously also applies to teaching the subject technology. However, lower secondary school technology education in Sweden has reportedly been described in terms of teaching not following the curriculum along with widespread uncertainty among teachers regarding how to design their teaching practices. To address this national challenge, we need to understand the existing technology teaching practice. The purpose of this study is therefore to explore the considerations experienced technology teachers make. The study is based on interviews with technology teachers who work in lower secondary school (13–15-year-old pupils). The collected data consist of teacher’s statements regarding their own expertise and teaching practice. To visualize the described teaching practice we have analysed collected data through the lens of pedagogical content knowledge (PCK). The results show both similarities and differences in the teachers’ descriptions. Speaking in terms of PCK, the purpose and teaching focus expressed by the respondents, framed within the category ‘Orientations to teach technology’, vary considerably. However, regarding ‘instructional strategies’, the consensus among those experienced teachers is striking. Experienced technology teachers’ teaching practices are proven to provide valuable information about the subject’s potential, and the findings offer a basis for the future development of the subject of technology as well as future teacher education and professional development courses.