ABSTRACT
The biocidal effect of Algophase (2,3,5,6-tetrachloro-4-methylsulfonyl-pyridine) has been tested against the sheated cyanobacterium Gloeothece membranacea Culture Collection of Algae and Protozoa 1430/3. Gloeothece membranacea is a cyanobacterium commonly found in biofilms on monuments. G. membranacea forms clusters with a dense extracellular polymeric substance (EPS) that helps its attachment to stone surfaces. Once attached, growth leads to accumulation of cell clusters surrounded by the EPS matrix like in a biofilm. EPS is involved in the resistance to physical and/or chemical treatments. Thus, the production of EPS can influence biocidal activity against biofilms on stone monuments. Gypsum regulates EPS synthesis due to accumulation of sulfate in its sheath. Also the presence of gypsum, common in the surfaces of urban buildings and monuments promotes the colonisation of degraded stones and causes changes in epilithic communities, favoring less sensitive and better adapted microorganisms, particularly those needing sulfate for growth and production of EPS.
