Lowering technical barriers in microbiology education using archaea: Halobacterium salinarum as a school laboratory...

Traditional microbiology education is fundamentally constrained by the requirement for sterile laboratory conditions, which limits the implementation of practical activities in school settings. This limitation can be overcome by using Halobacterium salinarum, a halophilic archaeon that grows readily on media containing up to 5 mol·l⁻¹ (290 g·l⁻¹) sodium chloride, effectively preventing contamination. Moreover, this micro-organism is non-pathogenic and well suited for educational use. This article presents two simple hands-on activities that can be easily carried out in a standard school science laboratory using common consumer products with the aim of reducing operational costs. The first activity introduces basic microbiological techniques by highlighting characteristic features of H. salinarum colonies, including their pink pigmentation and violet fluorescence under UV light. The second activity involves microscopic observation of cells stained with crystal violet, using microscope slides prepared according to a protocol adapted for halophilic microorganisms. Well-stained, flexible rod-shaped cells are observed, reflecting the absence of a rigid cell wall. Following these activities, a short questionnaire is proposed to encourage reflection on the experimental work performed. Instructors are also invited to discuss with students the role of extremophiles in the evolution of life forms.