Weathering of granitic gneiss: A geochemical and microbiological study in the polluted sub-tropical city of Rio de Janeiro.

Chemical and biological weathering were studied on two historic churches in the city of Rio de Janeiro, Brazil. The churches exhibited contour scaling, granular disintegration and black crust development. High levels of SO were found in façade stones of one church, São José, with significant levels of lead and copper.

Design and synthesis of four steroid-oxirane derivatives using some chemical tools.

This study involved the synthesis of several new derivatives of progesterone, 11a-hydroxyprogesterone, 11a-t-butyldimethylsilanyloxyprogesterone, and andrenosterone. The new derivatives were prepared by condensation of the 4-en-3-one moiety of the four steroids with 2-hydroxy-1-naphthaldehyde to afford a series of 4-(R)-hydroxy-(2-hydroxynaphtalen-1-yl) adducts. These adducts were further modified by cyclization reactions of the dihydroxynaphthalenyl moieties with succinic acid, and the resulting cyclic succinates were then condensed with ethylenediamine to form imine derivatives at all available carbonyl groups.

Microbial biofilms on the sandstone monuments of the Angkor Wat Complex, Cambodia.

Discoloring biofilms from Cambodian temples Angkor Wat, Preah Khan, and the Bayon and West Prasat in Angkor Thom contained a microbial community dominated by coccoid cyanobacteria. Molecular analysis identified Chroococcidiopsis as major colonizer, but low similarity values (<95%) suggested a similar genus or species not present in the databases. In only two of the six sites sampled were filamentous cyanobacteria, Microcoleus, Leptolyngbya, and Scytonema, found; the first two detected by sequencing of 16S rRNA gene library clones from samples of a moist green biofilm on internal walls in Preah Khan, where Lyngbya (possibly synonymous with Microcoleus) was seen by direct microscopy as major colonizer.

Microbial deterioration of stone monuments--an updated overview.

Cultural heritage monuments may be discolored and degraded by growth and activity of living organisms. Microorganisms form biofilms on surfaces of stone, with resulting aesthetic and structural damage. The organisms involved are bacteria (including actinomycetes and cyanobacteria), fungi, archaea, algae, and lichens.

Characterization of sulfate-reducing bacteria dominated surface communities during start-up of a down-flow fluidized bed reactor.

An anaerobic down-flow fluidized bed reactor was inoculated with granular sludge and started-up with sulfate containing synthetic wastewater to promote the formation of a biofilm enriched in sulfate-reducing bacteria (SRB), to produce biogenic sulfide. The start-up was done in two stages operating the reactor in batch for 45 days followed by 85 days of continuous operation. Low-density polyethylene was used as support.

Biogenic black crusts on buildings in unpolluted environments.

Samples of peeling black crusts from modern and historic buildings in Campeche, Mexico, from a gravestone on the island of Dom Khon, Lao, and from the Anglican cathedral in Belize City were analyzed microbiologically, by scanning electron microscopy plus electron dispersive spectroscopy (EDS) and for pigment composition. In all cases, the surface was covered by a thick mat of cyanobacteria with dark brown sheaths. These were filamentous organisms of the genera Scytonema or Fischerella/Mastigocladus, except for one sample, where coccoid cyanobacteria of Subsection II were predominant.