Factors affecting bacterial growth pdf

AIntrinsic factors: These are inherent in. Nutrients, temperature, water activity, pH, chemical inhibitors, and atmosphere all can be used to control growth. Both factors: surplus of easily available C and. Temperature, the most important factor affecting the efficacy of antimicrobial.

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Tawanda Charumuka. Candy Kim. Tuan Anh. This margin generally retains the color of the thallus and normally contains algal cells. In lecideine apothecia, the exciple is part of the true apothecial tissue and does not contain algal cells. Discs that become very contorted and appear as line segments on the surface of the thallus are called lyrellae. At maturity, an apical opening, the ostiole, releases the ascospores. Perithecia are usually partially embedded in the thallus or in the substratum and are relatively small, rarely more than 1 mm in diameter and commonly much less.

Pinna The susceptibility of stones to hold organisms is called bioreceptivity, a term coined by Guillitte There are several reports in the literature on studies conducted either in situ or under laboratory conditions on the assessment of bioreceptivity. Highly porous materials are more susceptible to microbial colonization because of their capacity to absorb more water and retain it in for longer periods of time. It also enables the accumulation of particles - soot, organic and inorganic debris, pollens, spores, and salts Jacob et al.

In addition, rougher surfaces can be a preferential site for colonization because they provide shelter from wind, desiccation, and excessive solar radiation Miller et al. Abrasion pH, measured after grinding the rock in distilled water, relates to the number of basic cations released by the rock when in contact with aqueous solutions. Open porosity is correlated with void spaces in the rock; thus, it refers to the capacity of rock to absorb water.

Capillary water absorp- tion, providing information about the pattern of the pore network, is connected to the time the rocks remain wet.

A study Miller et al. The result apparently depends mainly on the chemical composition rather than on the physical characteristics of the stones. Similarly, the importance of stone chemical composition emerged from a laboratory experiment Olsson-Francis et al.

According to the authors, the difference is due to a higher content of quartz, which has a low rate of weathering, and to lower concentrations of bio-essential elements, such as Ca, Fe, and Mg.

The 8-year-long study showed that the recolonization of the three substrata after the cleaning depended mainly on their bioreceptivity and on climatic conditions. Marble showed a high bioreceptivity as, at the end of the monitoring, fungi and lichens covered the surfaces. On the contrary, sandstone and plaster showed very low bioreceptivity. Unlike marble, the pioneer species on sandstone were lichens that started developing more than 4 years after cleaning.

At the end of the monitoring, the lichens grew extensively on sandstone surfaces, but did not cover them completely.

Although the position near the ground of the test area of the original Roman plaster would be expected to be favorable to biological growth, it was the least bioreceptive substra- tum as, at the end of the monitoring, almost no biological colonization was detected on the surfaces. It showed a low water absorption due to the presence of cocciopesto,1 of a natural wax, and of an outer thin whitish calcite layer.

As the environmental conditions of the tested areas did not differ and the porosity was quite low on all the stones, arguably the different bioreceptivity can relate to their chemical composition, pH, shape and orientation of pores, pore size distribution and surface texture.

Different types of stone show different bioreceptivities toward lichen coloniza- tion as it has been shown in a study of gravestones in Jewish urban cemeteries in north-eastern Italy Caneva and Bartoli Trachyte mainly hosted the growth of the lichen Protoparmeliopsis muralis which covered horizontal surfaces. Verona stone, marble, and Istrian stone were less colonized while Nanto stone, a soft yellow- brown limestone, was the material mostly affected by lichen colonization, and suffered the highest degree of deterioration.

Although most microorganisms tend to live in pH neutral conditions, some may colonize cement over a wide pH range Allsopp et al. Many fungi prefer slightly acidic substrata e. As a fresh concrete has a pH of 12—13, it permits microbial growth when pH is lowered by reaction with atmospheric carbon dioxide carbonation Allsopp et al. The alkalinity of concrete is crucial to decrease the rate of biodeterioration by inhibiting the microbial activity Noeiaghaei 1 Cocciopesto is a decorative plaster dating back to Roman times.

Pinna et al. Thus, the degree of carbonation and pH values play a key role in the receptivity of concrete and mortars to microbial colonization. Differences in abundance of colonization on stones can be due to tertiary bioreceptivity related to nutrients contained on the surfaces or in the stones Salvadori and Charola They can derive from existing biological growth on the surface, bird droppings, organic compounds used in restoration practice, pollut- ants.

Air and rain carry nutrients in the form of dust and soil particles. Soil fertilization leads to an accumulation of nitrates and phosphates eutrophication that are contained in bird droppings too. Some lichens nitrophilic species have been adapted to high nitrogen levels.

The extent of microbial growth was much broader on northern and western exposures respect to south-exposed walls. A similar study documented that the moisture contents in the walls of a brick tower was higher near the edges of the walls than at the center just for wind-driven precipitation, inducing fungal mold colonization especially at this position Abuku et al.

In these studies, the orientation of the object towards the light was an aspect affecting microbial colonization as well. In wet climates and northern latitudes, north-exposed surfaces get less direct sunlight.

Therefore, once wet, they remain damp for much longer than other stones. This slow-drying condition is much more favorable to biological colonization than the hostile condition of rapid wetting and drying cycles experienced on the south faces Adamson et al. Similarly, in a different climate and latitude south of Brazil painted surfaces showed higher fungal coloni- zation on south-facing sides that received less solar radiation than north-facing ones.

If the surface temperature fell below dew point at night, they remained moist for longer periods of time after wetting Shirakawa et al. Most of them may be grouped into three categories on a thermal basis.

Temperature may also affect the stone water content. Areas with lower temperatures were, on average, greener than warmer areas. As reported by the authors, it is possible to model algal greening of sandstones from the scaled-down outputs of regional climate models as it mostly relates to climate and atmospheric particulates. In hot climates sunny surfaces are more hostile and variable than those shaded, thus the production of extra cellular polymeric substances tends to be higher to protect the cells from the adverse conditions Scheerer Since these weathering processes interact and enhance each other action, it is impossible to separately quantify their role Bjelland and Thorseth ; de Los Rios et al.

Biomineralization produced by fungi occurs when they modify the local microen- vironment creating conditions that favor extracellular precipitation of mineral phases Fomina et al. Stone-inhabiting microorganisms may grow on the surface epiliths or some millimeters or even centimeters in the substratum endoliths Gadd et al. The use of the substratum as a shield against external stress proves to be a decisive evolutionary selection advantage Pohl and Scheider This process can occur repeatedly, involving areas increas- ingly in depth Pinna and Salvadori The light that reaches the bulk of the stones limits the growth of phototrophic microorganisms.

Euendoliths form microcavities of varying morphologies according to the species. Stones subjected to extreme sun irradiation in hyper-arid Atacama Desert Chile are colonized by endolithic algae and cyanobacteria. In order to endure the harsh environment, they synthesize carotenoids and scytonemin, respectively. Algae form colored green, gray, black, brown, and orange powdery patinas, and gelatinous layers.

They usually dominate surfaces in wet and rainy areas. Cyanobacteria typically form dark brown and black patinas but also pink discolorations. Besides the aesthetic disturbance caused by the colored patinas, algae and cyanobacteria cause water retention and damage due to freeze—thaw cycles.

The main groups of fungi isolated from stone monuments are Hyphomycetes and black meristematic fungi Salvadori and Casanova Hyphomycetes, com- monly known as mold, are a class of asexual or imperfect fungi. They lack fruiting bodies, the sexual structures used to classify other fungi. The production of conidia spores occurs by fragmentation of vegetative hyphae or from specialized hyphae called conidiophores.

Many Hyphomycetes, notably Aspergillus, Fusarium, and Penicillium genera, produce toxic metabolites mycotoxins. Several Hyphomycetes growing on stone heritage objects are dematiaceous. The term refers to the characteristic dark appearance of these fungi that form dark gray, brown or black colonies.

Fungi excrete organic acids oxalic, citric, acetic, formic, gluconic, glyoxylic, fumaric, malic, succinic, and pyruvic that can act as chelators. Particularly, oxalic acid has a high capacity of degrading minerals for its complexing and acid properties. The reaction results both in mineral dissolution and in mineral forma- tion Gadd et al. An investigation into a thin dark rock coating at the Ngaut Ngaut heritage complex in South Australia showed that it contained a mixture of calcite, quartz, gypsum, and weddellite Roberts et al.

The dark coating covered petroglyphs engraved in the rock shelter and dated back around years B. Metal mobilization can also be achieved by chelation ability of siderophores. When living in environments of reduced iron content, fungi produce iron III - binding ligands, commonly of a hydroxamate nature, termed siderophores Salvadori and Casanova Their cells have thick pigmented walls. In addition to the meristematic growth, many of the black fungi can exhibit a yeast-like growth De Leo et al.

They abandoned the hyphal phase adopting the microcolonial or yeast phase characterized by an extremely slow growth, in response to the lack of organic nutrients and to stresses of outdoor substrata. They produce various pigments including carotenoids, mycosporines, and melanins that protect them from UV irradiation. Peculiar pattern of stone weathering on a sample.

Stereomicroscope b. Polished cross section of the sample showing black fungi on the surface and hyaline hyphae in the bulk of the stone c and lichens, are poikilohydric microorganisms, which means that they are metabol- ically active or dormant depending on water availability. They can thrive under extreme conditions including irradiation, temperature, salinity, pH, and moisture.

They are stress-tolerant colonizers involved in biodeterioration de los Rios et al. On marbles, they grow in the inter-crystalline spaces Fig. Biopitting is an alteration caused by euendolithic microorganisms that form little blind holes close together Golubic et al. In the history, they have been made using several techniques.

The pigments are absorbed by the wet plaster. Close-up of a detail of the surface right. The circular micro-holes were likely produced by endolithic lichens that grew when the statue was located outdoors.

The fruiting bodies were present inside the holes. After the lichens died, they left just the empty holes Italian. In Classical Greco-Roman times, the encaustic painting technique was in use. Pigments were ground in a molten beeswax binder or resin binder and applied to the surface while hot.

Today, murals are mostly painted in oils, tempera, or acrylic colors. Oxalates may be produced from the calcite or from metal-containing pigments of the painted layers Gadd et al. The deteriorative potential of fungi isolated from wall paintings was evaluated by in vitro studies to assess the risk of deterioration and formulate appropriate conser- vation treatments.

Many species of the genera Aspergillus and Penicillium demonstrated the ability to dissolve calcite as they produced and secreted acids; oxalic acid was the main cause of deterioration in most instances Ortega-Morales et al.

They are thought as the primary degraders of protein components of painted layers of wall paintings. Applying the mentioned method, the authors detected also species show- ing no deterioration capabilities.

Pink patinas and rosy discolorations occurring on stones and wall paintings may be caused by bacteria and algae. In the crypt of the Original Sin Matera, Italy , the pink color resulted from the production of a ruberin-type carotenoid pigment produced by actinobacteria Nugari et al. Similarly, carotenoids caused pink and yellow discolorations on wall paintings of St. According to the authors, the pigments provide microorganisms with a protective mechanism against damage caused by photooxidation reactions.

Rosy-powdered areas on the frescoes of St. An analogous alteration on wall paintings of two churches in Georgia Gittins et al. Green algae belonging to the genus Trentepohlia formed red powdery spots on a medieval wall painting in Italy Zucconi et al. Then the paintings suffered from a fungal invasion by Fusarium solani which formed long white mycelia, and by dematiaceous fungi which produced black stains on the ceiling and passage banks Bastian et al.

These problems, which generated world- wide interest because the prehistoric drawings represent a priceless cultural heritage for all humankind, led to the closure of the cave in A similar case was that of the wall paintings of Takamatsuzuka Tumulus Japan discovered in Miura The temperature of the tomb was quite stable until , when it began to rise following the outdoor temperature.

Several brown spots were spread on the wall paintings of the tomb of King Tutankhamun Valley of the Kings, Luxor, Egypt when it was discovered in Szczepanowska and Cavaliere The perspiration and breathe of visitors were a further source of moisture. According to a report by the Getty Conservation Institute www. The paleolithic cave of Altamira in Spain was close to the public in after photosynthetic bacteria and fungi deteriorated the prehistoric paintings Jurado et al.

Pinna cause of damage. A progressive deep- ening of their growth in the substrata leads to the mobilization of elements and to higher water retention by polysaccharide sheaths. Mineral crystals were observed on the cells of some cyanobacteria Scytonema julianum and Loriella sp. As reported by the authors, Streptomyces, associated to S. A white crust formation is generally associated to the deposition of these crystals and it results in a stromatolitic layer on the stone surface.

Calcium carbonate dissolution and precipitation are the main processes in the biotransformation of calcareous substrata in caves Albertano et al.

Actinobacteria produced extracellular pigments that caused color change of the wall paintings located in the Snu-Sert-Ankh tomb, Egypt Elhagrassy Zammit et al.

Biodeteriorative effects of lichens on stone cultural heritage objects are well documented. However, they varied considerably from species to species.

The mechanisms involved in the weathering have been mentioned above. Lichens produce hundreds of carbon-based secondary substances so-called lichen sub- stances , most of which are unique to the lichen symbiosis. Depending on their chemical structure, they can act as complexing agents. One of the organic acids produced by lichens is oxalic acid, a strong complexing agent, as it has been discussed.

It forms chelating bonds producing calcium, magnesium, manganese, and copper oxalate crystals at the rock—epilithic lichen interface, in the thalli, on their surface, and in the bulk of the stones down to the depth reached by fungal hyphae Edwards et al. Oxalates have been implicated in Fe, Si, Mg, Ca, K, and Al mobilization from sandstone, basalt, granite, limestone, and silicates Gadd et al.

Dirina massiliensis f. Hyphae may develop into calcite up to 20 mm and calcium oxalate is present within the stone Salvadori and Casanova In a medieval cave exposed to external environmental conditions this lichen grew on wall paintings and its gray-green powdery thalli formed a compact and continuous crust that included materials derived from the paintings. The decay and detachment of the center part of the thallus occur in other lichen species and open the underlying area to further weathering, resulting in cratered mounts on the rock surface Mottershead and Lucas Endolithic lichens develop their biomass in the bulk of the stones, with coloni- zation patterns varying among species.

A different, atypical pattern of growth is that of Pyrenodesmia erodens, an euendolithic lichen able to dissolve limestones to a depth of several millimeters.

The clusters are arranged in bores formed by dissolution of the rock. This lichen has been found in dry sites of the Mediterranean region and of the southern Alps on exposed, subvertical faces of limestone and dolomite rocks Tretiach et al. The study focused on the lichen colonization and deterioration patterns in the semi-arid conditions of the area.

Besides the effects of Pyrenodesmia erodens, other epilithic and endolitihic lichens showed damaging action such as pitting and granular disaggregation. There- fore, lichen communities are a potential threat for the conservation of the archaeo- logical site. Moreover, lichen colonization and deterioration patterns do not appear peculiar respect to what has been previously described by the literature about colonized limestones in temperate and semi-arid areas around the Mediterranean basin.

The chemical deterioration of silicate and carbonate rocks by endolithic lichens relates to the secretion of siderophore-like compounds and of carbonic anhydrase Favero-Longo et al.

However, the study of calcium carbonate deterioration by endolithic lichens needs further experimental evidence and it is an interesting goal for further research.

The present results, yet relevant, enlighten the complexity of the phenomenon. When lichen death occurs, the empty pits are progres- sively enlarged by water rainfall, water runoff, water accumulation. Then they can coalesce forming larger interconnected depressions. Unlike epilithic species, endo- lithic ones are not characterized by the production of calcium oxalates. A one-year long laboratory experiment on lichen—rock interactions was conducted using mycobionts and photobionts of the endolithic lichens Bagliettoa baldensis and B.

They were isolated and then inoculated on marble and limestone samples. The same species growing on lime- stone outcrops and abandoned marble quarries showed penetration pathways similar to those reproduced in vitro. Pinna lichen development increased the availability of hyphae passageways only after long-term colonization. The differences in hyphae growth depended on the mineral composition and structure of the lithotypes.

Different climates affect the endolithic growth of lichens Pohl and Scheider In the humid Northern Alps Austrian glacier , the bulk of the calcareous rock, just under the surface, showed three layers. Then several mm in depth, there is the mycobiont with hyphae actively solubilizing the substratum and often forming dense networks.

The average colonization intensity and growth depth are markedly deeper in the more humid substratum of the Austrian Alps. To color the glass, powdered metals are added to the mixture while the glass is still molten. The medieval stained-glass windows that decorate many European churches were made using, besides sand, a different ingredient, the so-called potash that is wood ash K2O, K-rich glass. These glasses are more easily decayed than Na-rich ones. Neither the inorganic composition nor the physical features of glass favor microbial coloniza- tion, but the organic residues of various origins, as dust deposits, dead microbial material, and bird droppings, can be a source of nutrients.

The deteriorative action of microorganisms on glass is a modest, slow, yet continuous process that can accel- erate its weathering. Research focused mainly on medieval stained-glass windows of European churches where corrosion, patinas, pitting, cracks, and mineral crusts occur.

Microorganisms may contribute to all these decay forms Carmona et al. Fungi showed less diversity than bacteria, and species of the genera Aspergillus, Cladosporium, and Phoma were dominant Carmona et al. Thus, historical glass windows are a habitat in which both fungi and bacteria form complex microbial consortia of high diversity.

The bacteria are genetically similar to those that cause mineral precipitation on stones. The chemical composition of the glass affects microbial development; copper contained in green glasses acts as an inhibitor Marvasi et al.