Scientists have observed how bacteria “eat” stones for more than two years

  Scientists have discovered that bacteria can indeed start and accelerate the process of weathering rocks into soil.
  The land area under our feet is huge, and it seems that it hasn’t changed. But how the soil was born has always been a mystery. The scientific community used geology and meteorology knowledge to explain this mysterious problem in the dimension of time. Rocks form soil through weathering reactions, but for humans, this process is difficult to observe.
  For a long time, people have believed that there are organisms involved in this process (life activities are almost everywhere on the earth), and scientists have theoretically confirmed this possibility. However, no one has ever really observed the existence of life in the common ferrosilicon continental rocks. After all, relative to the career of a scientist, the weathering reaction of rocks is too long.
  Easily weathered rocks
  Nevertheless, the University of Wisconsin-Madison, a group of scientists at Bristol University and Pennsylvania State University decided to conduct an experiment for a period of 2.5 years, the study of microbial viability on this type of rock. In order to achieve this, they must come up with ways to speed up the process of rock weathering.
  One way is to find rocks that weather quickly. They did find the Rio Blanco Quartz Diorite (Rio Blanco Quartz Diorite) bedrock located in the Rio Icacos basin, which weathered abnormally fast. The researchers realized that this might be an ideal research sample that would allow them to complete the experiment within the planned time. Scientists collected pure samples of bedrock from a cutting, the soil and the rocks below it. There is also a transition zone between these soil and rock areas. Here, the fractured bedrock alternately exists with newly formed soil. This area has a strange name called “rindlet” zone.
  Scientists have discovered that in the deepest layer of soil, the abundance of ATP (a compound produced by cell metabolism) is second only to the surface layer of soil. This also means that there must be some life activities at the bottom of the soil, but what exactly is it?
  Source of electrons
  If there is indeed a biological weathering reaction, will electron transfer be involved in this process? An electron is a negatively charged particle that can move around the nucleus. The number of electrons in an atom changes frequently. An atom containing more electrons will be in a reduced state, and an atom containing fewer electrons will be in an oxidized state.
  All organisms need to obtain electrons to maintain life activities. They usually obtain electrons from sugar and other reduced organic compounds (that is, food), and then use these electrons to generate energy in cell respiration. Some microorganisms can also use simple inorganic compounds or atoms as a source of electrons. The organisms that use stones as a source of electrons are called chemoautotrophic bacteria, and they eat rocks for a living.
  Minerals rich in reduced iron, such as pyrite, biotite, and hornblende, are potential food for bacteria. Due to the deprivation of electrons, these minerals can undergo a chemical decomposition process-that is, weathering, accompanied by a change in appearance. This change should be observed under a microscope. Therefore, the scientists brought the more weatherable rocks and soil containing microorganisms back to the laboratory and grind the rocks to increase their surface area. Later, they mixed these rocks with microorganisms.
  Rock into soil
  30 months later, they put a sample under a microscope. After culturing with microorganisms for 864 days, these rocks appeared jagged and pitted, as if they had been corroded by acid, as shown in Figure 1. In contrast, the rock in the control group (without microorganisms) retained sharp, smooth edges, as shown in Figure 2.
  They detected an abundance of ATP in a mixture of rocks containing microorganisms, which indicated that they were enjoying “food”–that is, these rocks. And another mystery is: Who is eating the rock? When they checked the DNA of the microorganisms in the samples, they found that these microorganisms were almost all bacteria, but no fungi. The researchers believe that either the amount of “food” in this area is not enough to support the survival of the fungus, or the culture conditions in their experiment cannot support the survival of the fungus originally present in the sample.
  In addition, they also found that these chemoautotrophic bacteria do have a special ability: to obtain electrons from outside iron atoms. These bacteria take up electrons through a method called extracellular electron transfer. This method has another advantage. These microorganisms can avoid the accumulation of oxidized iron atoms in the body, thereby avoiding a potentially fatal threat. Therefore, bacteria can indeed start and accelerate the process of weathering rocks into soil. The soil on the land breeds plants, and plants support almost all other life.