The "magic weapon" used by microorganisms to communicate is actually an accomplice of blue-green algae blooms?

Produced by: Science Popularization China

Author: Flower Tea (Qingdao Agricultural University)

Producer: China Science Expo

Editor's note: In order to decode the latest mysteries of life science, the China Science Popularization Frontier Science Project has launched a series of articles called "New Knowledge of Life" to interpret life phenomena and reveal biological mysteries from a unique perspective. Let us delve into the world of life and explore infinite possibilities.

In the vast natural world, microorganisms are dotted in every corner like stars. Although they are tiny, they have amazing wisdom and strong adaptability. They have evolved a communication that only microorganisms can "hear" - "quorum sensing" (QS). Scientists have conducted in-depth research on this mechanism, revealing the great wisdom of microorganisms, and won the 2016 Nobel Prize in Physiology or Medicine. Now, let us walk into this silent "dialogue" between microorganisms and explore the mystery of quorum sensing.

Microbial quorum sensing is like a greeting communication between microorganisms

(Photo source: veer photo gallery)

Silent "dialogue"

In a busy city, people transmit information and coordinate actions through mobile phones, radio or face-to-face communication. In the microscopic world, bacteria are not lonely rangers, they also have their own "communication method", which is group sensing.

Quorum sensing is a communication mechanism by which microorganisms adjust their behavior by sensing the number of similar microorganisms in the surrounding environment . When the density of microorganisms reaches a certain threshold, they will initiate a series of changes in gene expression. This cell density-based communication mechanism allows bacteria to sense the presence of their companions and coordinate their behavior, affecting their growth, metabolism, virulence and other factors.

Imagine that it is like bacteria having a big party, and the party will not start until a certain number of people have joined. This is like a silent "conversation" between microorganisms. Although there is no sound, it is full of wisdom and strategy. This kind of communication is crucial for them to better adapt to the environment and improve their survival ability, and it is of great significance in many scenarios and states.

Quorum sensing helps the formation of biofilms , which are an important survival strategy for microorganisms in harsh environments. Biofilms can also be seen as the "armor" of microorganisms. They are composed of a large number of bacteria and extracellular products, forming a three-dimensional structure of the community. Through quorum sensing, microorganisms can cooperate with each other to build this complex structure and enhance resistance to the environment and antibiotics.

Microbial biofilm formation

(Photo source: veer photo gallery)

Quorum sensing can also regulate the production of virulence factors of pathogenic microorganisms. For pathogenic microorganisms, virulence factors are their key weapons to infect hosts and cause diseases. Quorum sensing is like the "arsenal manager" of these microorganisms, responsible for regulating the production of these virulence factors. When the density of microorganisms increases, quorum sensing will prompt them to produce more toxins, enzymes and other harmful compounds, exacerbating the infection, similar to increasing the number of troops and firepower on the battlefield, making the situation more favorable to the microorganisms.

Horizontal gene transfer is one of the important means for microorganisms to quickly adapt to environmental changes. Within the bacterial community, through quorum sensing, microorganisms can more efficiently exchange and recombine genes, thereby acquiring new genetic characteristics, just like participating in a "gene carnival party", learning from each other and strengthening themselves.

Quorum sensing also helps maintain the stability of microbial populations , acting like a "census taker" in the microbial world. It monitors changes in population sizes and sends signals to adjust the number of microorganisms to ensure that everything is under control.

Good news for microbes, bad news for humans

Although quorum sensing is an important survival strategy for microorganisms, it also brings a lot of trouble to us humans:

The most difficult problem is drug resistance. With the widespread use of antibiotics, more and more pathogenic microorganisms have developed drug resistance, and quorum sensing may aggravate this phenomenon, allowing microorganisms to enhance their drug resistance through a series of gene expression changes. This is an "arms race" between microorganisms and humans, and there is no end to it.

In addition, quorum sensing can also increase the production of virulence factors of pathogens, thereby exacerbating infections. For example, Pseudomonas aeruginosa, one of the most common pathogens, produces more toxins at high density, like microorganisms suddenly gaining a "secret weapon" on the battlefield, making the battle more intense and cruel, and ultimately resulting in more severe lung infections.

From an ecological perspective, quorum sensing may also lead to abnormal proliferation of microorganisms in water and soil, causing environmental pollution problems. For example, algae blooms are caused by excessive algae growth due to quorum sensing. This not only affects water quality and ecological balance, but also poses a potential threat to human health.

Treat others the way you want them to treat you

Scientists are actively studying ways to control quorum sensing to protect human health and environmental safety. They are drawing on strategies to block infectious diseases to address the regulation of quorum sensing systems.

Since signal molecules are the key mediators of quorum sensing, quorum sensing can be prevented by inhibiting the production of signal molecules. Scientists screen or synthesize specific enzymes and chemical drugs to inhibit the expression of signal molecules at the molecular level.

In addition, we can also prevent microbial communication by interfering with signal transmission. Imagine if we could find a "signal jammer" to make the communication between microorganisms chaotic, then it would be difficult for them to form an effective attack force. Scientists try to use antibodies or small molecule compounds to block the reception function of signal receptors, which is equivalent to setting up "roadblocks" on the communication lines of microorganisms, making their information transmission difficult.

When scientists are looking for candidate drugs, they draw on natural products in nature that have the ability to inhibit quorum sensing. These substances, such as allicin and tea polyphenols, can inhibit the activity of quorum sensing-related enzymes. In addition, with the development of gene editing technology, we can now reduce the quorum sensing ability of microorganisms by knocking out or mutating genes related to quorum sensing. This method has achieved certain success in the laboratory, and in the future it is expected that a new type of microorganism that is both beneficial and safe can be created through gene editing technology.

Natural antibacterial active ingredients

(Photo source: veer photo gallery)

Reasonable use and harmonious coexistence

As an important communication mechanism between microorganisms, quorum sensing has a significant impact on microbial growth, metabolism, and virulence. However, it may also lead to problems such as drug resistance, increased pathogenicity, and environmental pollution. Therefore, researching and developing effective control strategies is of great significance to safeguard human health and environmental safety.

As the scientific community has a deeper understanding of quorum sensing, the quorum sensing system has become a new control target for pathogenic microorganisms. In particular, everyone has realized that simply killing bacteria may cause the emergence of super bacteria, and what really needs to be solved is the pathogenicity of bacteria. Therefore, the development of new inhibitors targeting quorum sensing mechanisms is becoming a research and development focus. These inhibitors can directly act on signal molecules or signal transmission pathways, thereby inhibiting the occurrence of quorum sensing.

Unlike traditional antibiotics, new antimicrobial agents do not have a direct killing effect on microorganisms. Instead, they weaken their pathogenicity by interfering with the communication mechanism between microorganisms. This is similar to the tactics of "psychological warfare", which makes the enemy lose their fighting spirit without knowing it, and will not cause fierce resistance from the enemy, thereby achieving harmonious coexistence between humans and microorganisms.