Recent conceptualizations of science literacy, a key aim of contemporary science education, suggest defining it as a function of actual uses of science in daily life. We characterize expressions of science literacy in online authentic public discourse, using content analysis of a year's worth of widely-read Israeli online news site coverage of animal experimentation and its reader comments, we explore how expressions of science literacy interact with coverage. The national Israeli science-curricula were used as an analytical framework, including scientific knowledge, nature of science (NOS), and inquiry skills. The findings indicate that over half of the scientific concepts used by the commentators are at the high school or academic level, in which science is elective. There were strong correlations (r = 0.96) between the level of overall science concepts used in the articles and reader comments. Comments supporting animal experimentation employed more and higher level of scientific concepts. Contrasting positions were supported by different types of NOS content: opponents of animal experimentation referred more to the social aspects of NOS, echoing differences in worldviews and lack of trust in scientists. We suggest that enabling informed public engagement with science requires explicit integration of investigative and social aspects of the nature of science.