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Microalgae and cyanobacteria are tiny, microscopic plant-like organisms that float in the water and grow using nutrients from the water, energy from the sun and carbon dioxide gas from the air. Most microalgae and cyanobacteria are helpful because, like grass for cows on land, they provide food for aquatic animals. However, some microalgae and cyanobacteria are poisonous and when large numbers of them occur, they are called harmful algal blooms, or HABs for short. HABs can poison both humans and animals through the food they eat, the water they drink, and even the air they breathe. HABs are increasing within lakes, rivers, oceans, and estuaries worldwide because of pollution and climate change. This article will tell you about HABs in San Francisco Estuary, USA: who they are, what they look like, why they occur, how they affect plants, animals and people, and things you can do as a HAB warrior to stay safe and prevent their spread. 

This work shines light on the role of extracellular polymeric substance (EPS) in the formation and preservation of elemental sulfur biominerals produced by sulfur-oxidizing bacteria. We characterized elemental sulfur particles produced within a Sulfurovum -rich biofilm in the Frasassi Cave System (Italy). The particles adopt spherical and bipyramidal morphologies, and display both stable (α-S 8 ) and metastable (β-S 8 ) crystal structures. Elemental sulfur is embedded within a dense matrix of EPS, and the particles are surrounded by organic envelopes rich in amide and carboxylic groups. Organic encapsulation and the presence of metastable crystal structures are consistent with elemental sulfur organomineralization, i.e., the formation and stabilization of elemental sulfur in the presence of organics, a mechanism that has previously been observed in laboratory studies. This research provides new evidence for the important role of microbial EPS in mineral formation in the environment. We hypothesize that the extracellular organics are used by sulfur-oxidizing bacteria for the stabilization of elemental sulfur minerals outside of the cell wall as a store of chemical energy. The stabilization of energy sources (in the form of a solid electron acceptor) in biofilms is a potential new role for microbial EPS that requires further investigation.