Bacteria and Art: Creation, Deterioration, and Preservation
Bacteria can play interesting roles in the creation, deterioration, and preservation of artwork. Bacterial processes can produce a wide spectrum of colored pigments that people have been able to isolate and extract for use in art. Scientists and artists alike are able to make artistic patterns with these bacterial pigments through selective bacterial culturing. These pigments can also be used in the coloration process of food, textiles, and paints. While bacteria can have a hand in the direct production of art, microbes can also pose significant threats to existing artwork. The presence and metabolic processes of microbes on art, particularly on ancient cave art, can cause serious deteriorative harm to the artwork. However, while bacteria cause these deteriorative issues, they can also help solve them. Certain bacteria are being used more and more in the restoration of art and may even be key in helping to prevent art deterioration in the first place.
Bacterial Pigment Production
Bacteria synthesize molecules of pigment in their cell wall or periplasmic space. The bacterial pigments produced can be water soluble or insoluble, but molecular oxygen is necessary for pigmentation so only aerobic bacteria are pigmented. However, pigment production is also dependent on factors like light, pH, temperature, and media. Pigmentation in bacteria occurs in association with morphological characteristics, cellular activities, pathogenesis, and protection. For example, pigments in photosynthetic bacteria carry out photosynthesis, similar to the way in which chlorophyll (a green colored pigment) functions in plants. Pigments in bacteria can also act to absorb UV radiation or other molecules in order to protect the cell.
Bacterial pigments can also be used as antibiotics, which target phytopathogenic fungi, bacteria, and yeasts, as well as human pathogens (G+ and G- bacteria and fungi). Bacterial pigments can protect the bacterial cell by conferring antibacterial and heavy metal resistance, by forming a barrier around the cell, which prevents antibiotics from interacting with the cell wall or membrane. Bacterial pigments can also act as biosensors of water, soil, and air pollution. In the 2009 International Genetically Engineered Machine Competition, a team from Cambridge developed E. chromi, a bacteria that expresses colorful pigments vivid enough to make bacterial art that were originally designed to act as environmental sensors (scientopia). Bacterial pigments can display a wide range colors, including all the colors of the rainbow and some unusual colors as well. This wide range of pigments bacteria produce can be used as food, textile, and paint colorants.
Examples of Bacterial Pigments
Purple: Spirillum rubrum
Violet: Chromobacterium violacein
Indigo: Janthinobacterium lividum
Blue: Streptomyces coelicolor
Green: Chlorobium tepidum
Yellow: Xanthomonas campestris
Orange: Sarcina aurentiaca
Red: Serratia marcescen
Brown: Rhiobium etli
Black: Prevotela melaninogenica
Golden: Staphylococcus aureus
Silver: Actinomyces sp.
White: Staphylococcus epidermidis
Cream: Proteus vulgaris
Pink: Micrococcus roseus
Maroon: Rugamonas rubra
Fluorescent blue/green: Pseudomonas aeruginosa
Fluorescent yellow: Pseudomonas fluorescens
Artificial vs. Natural Pigments
While bacteria are a potential source of pigments, these pigments must be isolated using solvent extraction, and then purified and characterized. Once extracted, bacterial pigments can be used for coloration. For example, the pigment of Streptomyces (Streptomyces coelicolor = bright blue) can be isolated and used to make paint. While some bacteria naturally produce these pigments, genes can also be added to certain bacteria in order to produce particular colors. Because E. coli is easy to grow, it is typically the bacteria that is modified in the lab and used to produce a wide variety of colors. The genes that have been added to E. coli enable the bacteria to make a wide variety of colored pigments.
Bacteria As Art
The patterns produced in response to certain conditions are one way in which bacteria can be used to make art. Alexander Fleming, who discovered Penicillin, grew different colors of bacteria for purely aesthetic reasons on agar dishes, using the bacteria to create distinct patterns and images. People have continued to produce this type of short-lived bacterial art, using easy-to-grow bacteria with genetically or artificially added pigments. The creation of artistic bacterial patterns takes place in the lab where an agar plate is inoculated with a droplet of 10,000 to 100,000 bacteria. Food for the bacteria becomes less prevalent as the bacteria multiply within the droplet, forcing the bacteria to send out branches across the plate in search of food. Scientists are able to vary the growth medium and conditions in the plate, thereby influencing the formation of these branches and the resulting bacterial patterns. These patterns may contain colored pigments, but colors can also be added artificially to the photographs of these patterns.
Biophysicists, while studying different bacteria in order to develop new antibiotics, are also observing the uniquely colored patterns produced by the bacteria and their pigments in the Petri dishes. The scientists are producing these patterns by varying the temperature and food sources in the Petri dishes and observing how the bacteria, despite difficult conditions, continue to grow. While they are trying to identify bacterial strategies for survival, they have also been able to create artistic patterns with the bacteria. They then turn these patterns into computer models that will hopefully allow them to create more effective antibiotics in the future.
Painting with Bacterial Pigments
Bacterial pigments can be used in painting by lifting the spores from the bacterial source with a paintbrush and applying them like paint to a Petri dish with a semi-solid agar medium. The spores are colorless at first so often an image is placed under the Petri dish to trace. When painting with bacterial pigments it is important to be aware of the antibiotics produced by each strain of bacteria that might battle with one another or inhibit each other if multiple strains of bacteria are being used to produce multiple colors. After the spores are applied the Petri dish has to be incubated, with pigments typically being produced after 2-3 days at 30 degrees Celsius. S. coelicolor can be used to make red and blue paint if the agar is broken into small pieces and water is introduced to the petri dish. Blue pigments will initially be produced, but by adding hydrochloric acid (vinegar), these pigments can be made red. Taking this ‘painting’ process a step further, Streptomyces can be used to produce pigmented molecules that can be isolated in pure forms and resuspended in a binder in order to make paint, which is extremely compatible with acrylics.
Impact of Bacteria on Existing Art
Degradation of Art
Bacteria are abundant on and pose a serious threat to ancient rock and cave paintings. The microclimate in these caves cannot be regulated as well as it can be in museums, with the result being that art that has survived for thousands of years in sealed caves is being destroyed in a matter of years by invasive bacterial species. Cave art paintings have been genetically tested for bacteria and have been shown to host a variety of unknown bacteria, some of which could be potentially harmful to these ancient paintings, which use the paintings as substrates during growth, produce destructive metabolites, or simply cover the paintings. The results of these tests suggest that new preservation measures need to be taken to ensure the longevity of the paintings, whose environment has already been altered significantly by the presence of tourists, who introduced foreign microbial populations, and artificial lighting, which led to the growth of algae and colonization by bacteria.
While previous testing indicated that a common soil bacteria is often found in cave wall colonies, tests on a red pigment from a 16,000 year old cave painting in Spain showed that this soil bacteria only accounted for about 5% of the bacterial community, while the rest contained acidobacteria, a bacteria that feeds on iron oxide, the major coloring element of red pigments in the caves. After the discovery of acidobacteria and proteobacteria at the caves at Altamira, Spain, authorities contemplated closing the caves to prevent further damage to the ancient art. While the actual impact of the strain of acidobacteria found is unknown at this point because it is difficult to culture microorganisms from natural environment and because 99% of the bacterial community in most caves goes undetected, the regular monitoring of the microbial community in the caves is essential. Leading preservation efforts focus on identifying what metabolic processes take place among the microbes existing in these cave paintings and what can be done to prevent said processes. Until these processes can be defined, caves with paintings are being closed off to visitors in an effort to return them to their natural states and prevent further degradation.
Besides those found in caves, many paintings are relatively unaffected by bacteria, because their placement in museums, where the temperature and humidity are highly regulated, helps to promote their preservation. In addition, the metals present in the components of their paint are toxic to many bacteria. However, some bacteria, those with higher heavy metal resistance, can still survive on these paintings and cause damage over time.
Bacterial Replacement of Paint
The ‘Bradshaw art’ in Western Australia has been shown to be colonized by bacteria and fungi that have kept the colors of the painting unusually vivid when compared to other ancient rock art that is facing problems with degradation caused by the growth of bacteria. Tests have shown that most of the paintings no longer contain paint, but instead show signs of life, helping to explain why attempts to date the Bradshaw art in the past have been difficult. The ‘living pigments’ in the rock art are made up of different species of bacteria whose inhabitation of the surface of the rock over millions of years has kept up the appearance of the painting surprisingly well. This may have occurred due to the presence of nutrients in the original paint that started the mutualism between the black fungi (which provides water) and red bacteria (which provides carbohydrates) that often accompany each other in the paintings. The species of microbes present in the paintings has not yet been discovered, but may help date the paintings using DNA sequencing in the future. While this bacterial infestation and its replacement of the original paint has proved beneficial in maintaining the appearance of the Bradshaw art, this is typically not the case with most art, which is damaged by the continual presence of bacteria. Rock art can be seriously damaged by “Desert Varnish,” a coating that occurs when clay-sized particles adhere to the rock surface. These particles often contain manganese and iron, and bacteria living on the rock surface are thought to oxidize the manganese, thereby damaging the artwork on the surface of the rock.
Bacterial Preservation of Art
While often harmful to artwork, bacteria can also be used in its preservation. The cellular activities of some bacteria, as well as their mere presence, can be used to discourage the growth of more harmful art-degrading bacteria. The presence of bacteria that have a minimal impact on the artwork helps ward off more harmful bacteria by physically taking up all the available space as well as by releasing chemicals that prevent the growth of other bacteria. Similarly, the addition of sulfate and nitrate reducing bacteria to wall paintings can actually minimize the amount of sulfur and nitrate available to other, more destructive bacteria, thereby decreasing the bacterial degradation of the art. Bacteria can also be used to restore works of art that are impacted by other problems. For example, a team of microbiologists and restorers are using a newly developed technique to remove salt buildups on frescoes in Valencia. The same technique has been used on sculptures and monuments. Strains of pseudomonas were trained to eat the saline efflorescence (salt buildup) that was obscuring the view of the painting. A similar method was used in Italy, where the organism was applied using cotton wool—the Valencia team took it a step further and developed a gel that can be spread on the frescoes that also prevents moisture from affecting the art. The gel is applied for an hour and a half, removed, and then the surface is dried and cleaned. With the removal of the moisture, the bacteria dies and can be taken off the fresco as well. Prior to the development of this technique, aggressive chemicals that were detrimental to both the art and restorers were used to clean the frescoes, and rust was eroded by mechanical means that harmed the paintings and took a long time to produce results. The use of bacteria in the restoration and preservation of art is a vast improvement over previous methods because it is less damaging to the art itself and not hazardous to restorers.
Bacteria in Art as a Preventative Measure
Scientists in South Dakota have recently developed a type of paint that is designed to kill disease-causing bacteria, including “superbugs” or antibiotic-resistant bacteria. While these new paints are intended for use in homes, businesses, and health care settings, its potential use in artwork in the future is interesting as well. While more research needs to be conducted on these new paints that are also capable of killing molds, fungi, and viruses, its use by artists could help protect their artwork, as it will suffer less degradation from harmful bacteria and require less restoration later on. These antimicrobial paints may be an important preventative measure in protecting artwork created by contemporary artists in the long term.
While the role bacteria play in the degradation of artwork is well documented, its use to create art, as well as to restore and preserve it, is still being researched. Further research may allow us to produce natural paints that serve as an alternative to synthetics and are more environmentally sustainable. As we increase our understandings of the ways bacteria interact with existing artwork, we will be better able to apply this knowledge to the preservation and restoration of art in both museums and in more unstable environments such as caves. Until then, scientists will continue to explore the complex ways in which bacteria interacts with art.
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Edited by (Kiersten! Abbie! Stephen! Tara!), students of Rachel Larsen in Bio 083 at Bowdoin College