The high-altitude brewery
In the high-altitude cold desert of Ladakh, traditional fermented beverages are a staple of the local diet. At elevations around 3,500 meters, communities prepare drinks like Chhang and Lugri, often made from barley or rice. These beverages are culturally significant and they are complex ecosystems with microorganisms. The fermentation process relies on a starter culture, locally known as 'phab', which contains a mixture of lactic acid bacteria (LAB), yeasts, and molds. This process happens under extreme environmental conditions: intense ultraviolet (UV) radiation, low oxygen levels, and drastic temperature fluctuations. These stressors have shaped the evolution of the microbial communities, resulting in unique strains adapted to survive where others cannot.
The dominant microbes responsible for the fermentation include yeasts like Saccharomyces cerevisiae and various species of Lactic Acid Bacteria such as Lactobacillus and Leuconostoc. These organisms are responsible for producing the alcohol and characteristic acidic flavors of the beverages. The specific composition of the microbiome varies, influenced by the grain used (rice, wheat, or barley) and the specific preparation techniques passed down through generations. For example, rice-based lugri often has a higher alcohol content and different microbial populations compared to its barley-based counterpart. This natural laboratory at high altitude has produced a reservoir of extremophilic microbes with unusual biochemical capabilities.
Extremophiles in a bottle
The microbes in Ladakhi fermented drinks are extremophiles, organisms that thrive in physically or geochemically extreme conditions. The intense solar radiation in Ladakh, with UV exposure increasing by 9% to 24% per thousand meters, presents a constant threat of DNA damage to these microorganisms. In response, these bacteria have developed highly efficient DNA repair systems. These systems are analogous to mechanisms found in other radiation-resistant organisms and involve several specialized pathways.
One such pathway is Nucleotide Excision Repair (NER), where a protein complex identifies a damaged section of DNA, snips it out, and replaces it with an accurate copy. Another is Ribonucleotide Excision Repair (RER), which corrects frequent errors that occur during the DNA copying process. These repair mechanisms are exceptionally robust in Ladakhi microbes. Studies on bacteria from high-altitude environments in the Himalayas have identified genes associated with UV-repair and oxidative stress functions. The microbial communities contain genera such as Lactobacillus, Bacillus, and Staphylococcus, which are known to possess strong DNA repair capabilities. These organisms survive the harsh UV conditions and contribute to the unique flavor profiles and potential probiotic qualities of the final beverage.