Integral and deep pedagogical content knowledge can support future primary teachers' ability to follow ideas of education for sustainability in science class. Initial teacher education provides opportunity to learn what and how to teach but still the practical experiences of teaching can reveal uneven development of student teachers' professionality. The aim of the study is to describe how future primary teachers reflect on their experiences about science teaching and what components of science pedagogical content knowledge they see as meaningful. A questionnaire and interviews were used. The results reveal the deep impact of teaching practice on students' understanding of the role of a teacher in supporting pupils' acquisition of scientific skills. The experiences described are related more to teaching and learning in general and less with science-specific factors. Nevertheless, students described changes in mission e.g. how they learned about their role through pupils' achievements and thinking about science. Changes in professional identity were mentioned rarely but this could point to an underestimated resource issue for teacher education. Positive changes in professional identity may help students to decide to choose more integral strategies in science teaching and thus promote more sustainability oriented teaching.