Wolfgang E. Krumbein

Microbially Induced Sedimentary Structures: A New Category within the Classification of Primary Sedimentary Structures

ABSTRACT Cyanobacterial films and mats syndepositonally influence erosion, deposition, and deformation of sediments. The biomass levels surface morphologies, and microbial mats stabilize depositional surfaces and shelter the sediment against erosion or degassing. Growing microbial mats dredge grains from their substrate upwards, whereas cyanobacterial filaments that are oriented perpendicular to the mat surface reach into the supernatant water and baffle, trap, and bind suspended particles. These and similar biotic-physical interactions are reflected in syndepositional formation of microbially induced sedimentary structures. We distinguish structures on bedding planes (leveled bedding surfaces, wrinkle structures, microbial mat chips, erosional remnants and pockets, multidirectional ripple marks, and mat curls) and internal bedding structures (sponge pore fabrics, gas domes, fenestrae structures, sinoidal laminae, oriented grains, benthic ooids, biolaminites, mat-layer-bound grain sizes). We propose to place this group of microbially mediated structures as a fifth category (bedding modified by microbial mats and biofilms) in Pettijohn and Potters (1964) existing classification of primary sedimentary structures.

Photolithotropic and chemoorganotrophic activity of bacteria and algae as related to beachrock formation and degradation (gulf of Aqaba, Sinai)

Beachrock formation and degradation along the shores of the Gulf of Aqaba (Sinai) were studied in the field and at the laboratory. Different types of beachrock were found, including laminated rocks. Rates of photosynthesis and respiration were studied under high‐and low‐tide conditions. Epilithic, chasmolithic, and endolithic bacteria, cyanobacteria, and algae were studied quantitatively. Bacterial contribution to carbonate precipitation and cementation was estimated in thin sections and by laboratory experiments. Precipitation of aragonite and monohydrocalcite was observed at salinities between 28‰ and 45‰. Concentrations of dissolved organic matter (DOM) and particulate organic matter (POM) were high at initial stages of beachrock formation and extremely low in final rock. Anaerobic and later aerobic decay processes initiate carbonate precipitation. A model is suggested that places beachrock as an intermediate between cyanobacterial influenced subtidal and su‐pratidal rocks. Formation, cementation, and ...

Stromatolites — the challenge of a term in space and time

Abstract Several definitions of stromatolites are discussed and Kalkowskys most important statements about stromatolites are translated from German to English. A new definition for stromatolites is proposed, namely “Stromatolites are laminated rocks, the origin of which can clearly be related to the activity of microbial communities, which by their morphology, physiology and arrangement in space and time interact with the physical and chemical environment to produce a laminated pattern which is retained in the final rock structure”. Unconsolidated laminated systems, clearly related to the activity of microbial communities and often called “recent stromatolites” or “living stromatolites”, are defined as “potential stromatolites”. The main microbial activities which are important in the formation of potential stromatolites and stromatolites are described and examples of stromatolites of various types, including iron stromatolites, are also described.

The simultaneous assay of chlorophyll and bacteriochlorophyll in natural microbial communities

A method to simultaneously determine chlorophyll a, bacteriochlorophyll a, their respective pheophytins and elemental sulfur is described. In addition, indications are obtained for the presence of other bacteriochlorophylls, even in the presence of chlorophyll a. Samples are extracted with methanol in the dark and shaken with hexane in a separatory funnel. Virtually all chlorophyll a and pheophytin a are found in the hexane phase, in addition to about 70% of bacteriochlorophyll a and its pheophytin. The other bacteriochlorophylls are more or less evenly distributed over both phases. Sulfur is found in the hexane phase only. The method has been applied to lab and field samples. It has proven very useful for estimating vertical distribution of pigments in laminated microbial ecosystems consisting of cyanobacteria and purple sulfur bacteria.

Nitrogenase activity in the non-heterocystous cyanobacterium Oscillatoria sp. grown under alternating light-dark cycles

The non-heterocystous cyanobacterium Oscillatoria sp. strain 23 fixes nitrogen under aerobic conditions. If nitrate-grown cultures were transferred to a medium free of combined nitrogen, nitrogenase was induced within about 1 day. The acetylene reduction showed a diurnal variation under conditions of continuous light. Maximum rates of acetylene reduction steadily increased during 8 successive days. When grown under alternating light-dark cycles, Oscillatoria sp. fixes nitrogen preferably in the dark period. For dark periods longer than 8 h, nitrogenase activity is only present during the dark period. For dark periods of 8 h and less, however, nitrogenase activity appears before the beginning of the dark period. This is most pronounced in cultures grown in a 20 h light – 4 h dark cycle. In that case, nitrogenase activity appears 3–4 h before the beginning of the dark period. According to the light-dark regime applied, nitrogenase activity was observed during 8–11 h. Oscillatoria sp. grown under 16 h light and 8 h dark cycle, also induced nitrogenase at the usual point of time, when suddenly transferred to conditions of continuous light. The activity appeared exactly at the point of time where the dark period used to begin. No nitrogenase activity was observed when chloramphenicol was added to the cultures 3 h before the onset of the dark period. This observation indicated that for each cycle, de novo nitrogenase synthesis is necessary.

Dematiaceous fungi as a major agent for biopitting on Mediterranean marbles and limestones

Experimental evidence is presented, for the first time, that dematiaceous fungi with yeast‐like growth patterns can actively penetrate rocks and cause loss of rock material, thus creating biopitting. Fungal strains inoculated onto Carrara marble cubes and submitted to alternating periods of humid and dry conditions produced biopits with a size of up to 500 fan within a period of 10 months. The type and geometry of biopits, however, were independent of the fungal genus causing the pit. Analysis of 22 field samples taken from monuments in the Sanctuary of Delos (Cyclades, Greece) demonstrated that biopitting is always found in connection with microcolonies of dematiaceous fungi, which penetrate the rock and form colonies on and in the rock. Based on these field observations and the laboratory experiments, a model for the mechanical attack of rock by dematiaceous fungi is proposed.

Contribution of microbial mats to sedimentary surface structures

SummaryThis paper summarizes studies of sedimentary surface structures in which microbial mats play a role. Intertidal/supratidal transitions of tidal flats of the North Sea coast, and shallow hypersaline water bodies of salterns (Bretagne, Canary and Balearic Islands), and Gavish Sabkha (Sinai) reveal a multitude of sedimentary surface structures which can be grouped and primary biologically controlled structures. Physically controlled surface structures include shrinkage cracks, erosion marks, deformation structures caused by water friction, gas pressure and mineral encrustation. Shrinkage cracks in microbial mats reveal the following features: (i) horizontally arranged cauliflower pattern that differs from the usually orthogonally regular crack morphology in clay, (ii) rounded edges and pillow-like thickening along the crack edges, caused by the growth of mats into the cracks. Criteria of erosion are pocket-like depressions and ripple marks on the thus exposed non-stabilized sand, and residual stacks of microbial mats. Deformation structures are due to water friction causing flotation of loosely attached microbial mats which fold and tear. Gas migration from deeper layers causes domal upheaval, protuberance structures, folds and “fairy rings”. Protuberance structures are caused by the rupture of gas domes and rapid escape of the enclosed gas. The sudden drop of pressure forces sediment to well up from below through the gas channels and to fill the internal hollow spaces of the domes. “Fairy rings” are horizontal ringshaped structures. Their center is the exit point of gas bubbles which escape from the substrate into the shallow water. The bubbles generate concentric waves which cause displacement of fine muddy sediments at the sediment-water interface Such gradual displacement guides mat-constructing microbes to grow concentrically. The “fairy rings” are crowned by pinnacle structures of bacterial and diatom origin. Pinnacles, “fairy rings” and pillow-like coatings of crack margins are biogenic structures which have to be genetically separated from purely physically controlled structures.

Nitrogen fixation associated with the cyanobacterial mat of a marine laminated microbial ecosystem

The nitrogenase activity in the cyanobacterial mat of a laminated microbial ecosystem was investigated by the acetylene reduction method. Measurements under several conditions such as light and dark, aerobic and anaerobic and by inhibiting photosystem II by 10-5 M DCMU showed the nitrogenase activity to be light stimulated and to some degree inhibited by oxygen. An appreciable amount of activity was also present under complete aerobic conditions. We estimated 8 to 15 kg N fixed per hectare per year for that part of the intertidal flat supporting growth of cyanobacteria. By measuring a vertical sediment profile, nitrogenase was shown to be associated with the cyanobacterial mat. Diurnal measurements of nitrogenase showed two activity peaks, one at sunrise and one at sunset. Following population dynamics in the cyanobacterial mat showed Microcoleus sp., Oscillatoria spp., Spirulina sp., Gloeocapsa sp. and sometimes Merismopedia sp. to be present. During four years of observations we never found any heterocystous cyanobacteria. Non-heterocystous cyanobacteria apparently play an important role in nitrogen fixation in this marine intertidal environment.

Interaction of marine sediment with DNA and DNA availability to nucleases

A method for the determination of DNA in sediments is described. The comparison between DNA extraction profiles from natural sediment samples and from precleaned sediments (concentrated nitric acid and subsequently 1 100 °C), to which known amounts of DNA were added, demonstrates that the sand particles participate in the delay of extraction of DNA we observed. Experiments with nuclease mixtures show that DNA by its interaction with the sediment is protected considerably against degradation by nucleases.

Biocorrosion and biodeterioration of antique and medieval glass

Abstract Over the past few years we have examined various antique and medieval glasses with regard to general biogenic damage, biopitting (crater erosion), bio‐crusts, and opalescent and white biogenic films. Experiments were carried out on pieces from Roman glass bottles excavated near Abu Tor, Sinai, some pieces of green and blue glass from Cologne Cathedral, some pieces from a little church in Evreux, glass samples from the fortress of the former Dukedom of Delmenhorst near Oldenburg, and some neolithic flint tools from the Negev Desert, Israel. Modern glass from a pigsty (19th century) additionally has been used for laboratory experiments on the attack of glass surfaces by fungi and bacteria. Some of the bacteria used in these experiments were isolated from the ancient pieces of glass. Biopitting with structures very similar to the biopitting of marble and limestone was found on almost all specimens. Lichens were not identified directly, but fungi and algae were observed in the pits as well as under t...