Acidic environments are flush with microbial life despite the harsh and extreme conditions. Scientists call these microbes acidophiles, which translates to “acid-loving.” These environments, such as the Yellowstone hot springs, sulfuric acid caves, and acid mine drainage, are also full of viruses. Like the flu virus infects humans, specific viruses infect bacteria. These viruses are called bacteriophages, which translates to “bacteria eaters.”
Scientists have previously reported that viruses are the most abundant biological entity on Earth. Viruses are not living organisms but they’ve been found in nearly all environments where life is present. However, scientists don’t fully understand their role in extremely acidic environments. Therefore, a team of scientists in China investigated the viral communities in acid mine drainage.
The scientists sampled 2 acid mine drainage sites in China. The Dabaoshan mine is a mine for several metals, and the Zijinshan mine is a copper mine. They confirmed both sites were acidic, with a pH of less than 3, and had high metal concentrations. They also identified diverse microbial communities in both sites.
The team wanted to see what factors impacted viral diversity and how viruses affected the variety of microorganisms. To do so, they analyzed all the DNA within samples collected from both sites. Then, they used specialized software to reconstruct the genomes and identify the microorganisms and viruses without having to grow them in the laboratory. This process is called metagenomics. The scientists also collected geochemical data like metal concentrations, pH, and temperature to measure how environmental conditions impacted microbial and viral communities.
The researchers found over 1,500 bacteriophages and other viruses in the acid mine drainage. They also found the most abundant viruses occurred where their hosts were abundant. This meant that as a certain type of microorganism increased in the environment, so did the viruses that infect it.
The researchers observed that some viruses provided benefits that improved the growth of the host microbes, at least temporarily. They reported that the viruses carried a specific gene that improved the uptake of necessary metals their bacterial host needed to grow. This improved growth gave the host a competitive edge within the microbial community. However, they remarked that this benefit costs a lot of cellular energy and only occurs when the microorganism is infected, which will ultimately lead to its death.
Lastly, the authors found that viruses and environmental conditions regulated the diversity and abundance of microbial communities in this environment. They reported that different environmental factors like metal content and acidity impacted both the microbial and viral communities, but the viral communities in the Dabaoshan mine had more impact on the variety of microorganisms present than the environmental conditions. Meanwhile, they found that both viral communities and environmental conditions within the Zijinshan mine similarly affected microbial communities there.
According to the team, this research expands the understanding of viruses within acidic environments. Currently, viruses from extreme environments only make up about 2% of the entire viral database, but these researchers showed that environments like acid mine drainage have numerous undocumented viruses. They also suggested researchers should consider the presence and contribution of viral “bacteria eaters” in other extreme environments, since bacteriophages may play a bigger role in regulating microbial communities than their local environment does.
