Widespread fungal-bacterial competition for magnesium lowers bacterial susceptibility to polymyxin antibiotics.

Fungi and bacteria coexist in many polymicrobial communities, yet the molecular basis of their interactions remains poorly understood. Here, we show that the fungus Candida albicans sequesters essential magnesium ions from the bacterium Pseudomonas aeruginosa. To counteract fungal Mg2+ sequestration, P. aeruginosa expresses the Mg2+ transporter MgtA when Mg2+ levels are low. Thus, loss of MgtA specifically impairs P. aeruginosa in co-culture with C. albicans, but fitness can be restored by supplementing Mg2+. Using a panel of fungi and bacteria, we show that Mg2+ sequestration is a general mechanism of fungal antagonism against gram-negative bacteria. Mg2+ limitation enhances bacterial resistance to polymyxin antibiotics like colistin, which target gram-negative bacterial membranes. Indeed, experimental evolution reveals that P. aeruginosa evolves C. albicans-dependent colistin resistance via non-canonical means; antifungal treatment renders resistant bacteria colistin-sensitive. Our work suggests that fungal-bacterial competition could profoundly impact polymicrobial infection treatment with antibiotics of last resort.

The story of a school participating in the Healthy School Award Scheme in Hong Kong.

This article described why the Tsung Tsin College joined in the Hong Kong Healthy Schools Award Scheme, how it tried to live up to the expectations, and the gains it reaped from the experience. Operating in a less affluent district of Hong Kong, the school strived for whole-person education for its students, many of whom suffer from social deprivations, and turned its environment into one conducive to learning. Finding that the Scheme advocates similar themes, the school enrolled and hoped to strengthen its self-improvement capacity. The school won a Silver Award for its overall performance in health promotion. The audit it underwent has also revealed its weaknesses, which it is striving to remedy. On the other hand, the school has also acquired many benefits from the process. The school-community and even school-parent relationships have also been enhanced as a result of its participation in the Scheme.