The Wadi Natrun: Chemical composition and microbial mass developments in alkaline brines of Eutrophic Desert Lakes

Six lakes of the Wadi Natrun, Egypt, were studied with respect to the chemical composition of their brines and the occurrence of microbial mass developments. All investigated lakes showed pH values of approximately 11 and a total salt content of generally more than 30%. The main components were sulfate, carbonate, chloride, sodium, and minor amounts of potassium. Only traces of magnesium and calcium were present, but unusually high concentrations of organic carbon compounds, nitrogen compounds, and phosphate were found. Mass developments of phototrophic sulfur bacteria, halobacteria, cyanobacteria, and green algae were observed. The functions of complete nitrogen and sulfur cycles in the alkaline brines are discussed. The properties of the lakes and their ecology are compared with data on the Dead Sea and Great Salt Lake, Utah.     

Microcolonial fungi from antique marbles in Perge/Side/Termessos (Antalya/Turkey)

In this study rock surfaces of archaeological sites in Antalya were investigated with a focus on black fungi for the first time. Black, meristematic fungi were isolated from surfaces of antique marble monuments in Antalya (Side, Perge, Termessos). Their morphology was characterized, their diversity was documented and the taxonomy and phylogeny of new isolates was clarified based on molecular methods, that is, by sequencing parts of the small ribosomal subunit (18S) and internal transcribed spacer (ITS) regions. From a total of around 250 samples 99 different fungal strains were isolated. In most of 99 strains the rDNA sequencing data and the lack of homologies in “Genbank” gave strong evidence that these strains have to be described as new species/subspecies and/or genera. All of them, however, clustered within the ascomycete orders of Dothideales, Chaetothyriales, and Pleosporales. Field studies show that these organisms cause color changes, black spots, crater shaped lesions as well as chipping and exfoliation of the rock surfaces in Antalya and thus they have to be regarded as a serious threat to the antique cultural heritage in Turkey.     

Biodeterioration of ancient stone materials from the Persepolis monuments (Iran)

The problem of deterioration of art works is particularly relevant in countries like Iran that are rich in cultural heritage. According to UNESCO data, Iran holds the tenth rank in a list of countries possessing the highest number of monuments belonging to the world cultural heritage. Archaeological areas, buildings, mosques, statues, museums and objects are all exposed to different biogenic and abiogenic stresses under generally aggressive climatic conditions. Lichens and fungi are known to actively decompose stone surfaces. This process is both physical and chemical in nature and often reaches deep below the stone surfaces. This is caused by chemical and physical interactions of the microbiota with the fluctuating and often drastically changing environmental conditions. Here, we describe and analyze the mainly physical degradation by invading fungal hyphae between stone crystals and a generally destabilizing stone texture. In addition to physical deterioration, organic acids produced by lichens enhance the chemical decomposing processes. In this work, penetration of hyphal bundles as well as individual fungi was studied, and the biodeteriorating patterns were documented and compared to general physical–chemical weathering phenomena. Several strains of aggressive black yeast-like fungi and bacteria were isolated and cultivated and will be described in a taxonomical context with many other isolates from different localities using physiological, morphological and molecular data.