Actinomycetes “enter the hall”, dozen tiger Pavilion Han tomb microbial outbreak

2022-06-08 0 By

The white plaque on the first Tomb of the Eastern Han Dynasty is worrying.Zhanhuting Han Tomb, located in Xinmi City, Zhengzhou city, dating back more than 1,800 years ago, is known as the “First tomb of the Eastern Han Dynasty in China” and was listed as a national key cultural relic protection site in January 1988.The stone carvings preserved in the Dahuting Han Tomb, such as Feast and Play and Tofu Making, record in detail the basic necessities of life of people in the Eastern Han Dynasty, and hold a high position in the history of Chinese archaeology and art.In recent years, however, white plaque has broken out on the walls of the han tomb in Dahuting.What these white spots are, where they come from, how they entered the tomb and how they “settled” and “multiplied” here have puzzled researchers.Since 2020, with the support of the key research and development project of the 13th Five-Year Plan of the Ministry of Science and Technology, Dunhuang Academy, Southeast University, nanjing Institute of Soil Sciences, Chinese Academy of Sciences (HEREINAFTER referred to as the Institute of Soil), together with a number of domestic and foreign research units,Field investigation, amplicon and metagenomic sequencing, physiological and biochemical identification of strains, and biological interaction experiments were carried out.Recently, published in the journal proceedings of the national academy of sciences of a “bright spot” article, the team presented the latest study found that the temperature and humidity of the dozen tiger pavilion in writing stable dark environment, attract springtails carry actinomyces into play to the underground chamber, and actinomycetes in the Chambers and a large number of breeding, let “bacteria stained” burial chamber walls.”This is the first study of ecological theory applied in the field of conservation microorganisms at home and abroad.”On March 30, Feng Youzhi accepted the science and technology daily reporter interview said.Feng, co-corresponding author of the paper, still remembers his first “consultation” at the Danhuting Han Tomb in July 2020, “when the murals and walls of the tomb were already covered with white plaque.”He recalls that the team collected white patches on the murals and soil samples from around the tomb, and measured the differences and similarities between bacterial and eukaryotic microbial communities. They found that the microbes in the tomb were dominated by actinomycetes and springworms, and came from the surrounding soil.”By monitoring the moisture and temperature changes in the burial chamber for six months, we found that the dark environment with stable temperature and humidity attracted springtails in the surrounding soil.”According to Feng youzhi, springtail is a kind of primitive insect, which is widely distributed in all kinds of soil and leaf litter around the world. After entering the tomb, they will live under bricks and stones. More importantly, the springtail also brings a “best friend” — actinomycetes.”Actinomycetes are prokaryotes that grow mainly as mycelium and reproduce by spores.Springtails and actinomycetes are mutually beneficial.”According to Feng, actinomycetes release a signaling molecule called geosmin, which attracts springtails to increase their dispersal capacity.In return, the antibiotics produced by the actinomyces increase springtails’ resistance to pathogenic microorganisms.After the actinomycetes “entered”, they began to build their own underground kingdom in the tomb.According to lead author Wenjing Liu, a PhD student at the Institute of Soil Sciences, actinomycetes have a strong ability to metabolize macromolecular substrates, making them more likely than other bacteria to colonize and grow on tomb walls or murals.At the same time, they can produce a variety of antibacterial substances, which inhibit the growth of other bacteria.Once actinomycetes proliferate in the crypt, geosmin will be released continuously, attracting more springtailed springworms to bring more actinomycetes into the crypt, which eventually led to the outbreak of microorganisms in the Han tomb in Dahuting.”This kind of white plaque is found in tombs and underground cavities, such as Lascaux Cave paintings in France and Altamira cave paintings in Spain.”Feng said that the study shows that the coordination of ecological processes, such as mutual benefit and competition of microbial species, is one of the important ways for the origin, migration, colonization and outbreak of the microbiome in burial sites, caves and other underground cultural sites.He believes that the combination of previous knowledge in microbiology and environmental microbiology will help scientists to understand, formulate and implement effective cultural protection measures.Source: Science and Technology Daily