City Adventures of Lactobacillus

In the middle of the night, in the fermentation tank of a yogurt processing factory in the suburbs of the city, I woke up from the vast ocean of milk, surrounded by an ocean of lactose, protein, and lactic acid. There are many different microorganisms floating in the ocean. I just woke up, can’t remember what happened before hibernation, and wandered aimlessly around. The lactic acid bacteria brothers and sisters beside them are all dormant. It seems that the concentration of lactic acid in this milk ocean is about to reach a critical value, which means that we have completed the mission of converting milk into yogurt. Where will I go next?

Explore the human gut
In the early morning, in the kitchen of the apartment building next to the street, the little boy took out bread and yogurt and prepared to eat his breakfast. And I am in this bottle of yogurt. The little boy drank the yogurt mixed with bread crumbs and drank it into the intestines. Under the stimulation of stomach acid, I woke up from a long sleep. Just when I was at a loss, there was a shout from the breadcrumbs. Not far away, I saw an elliptical older brother who was much larger than me. He swam towards me, “You are the lactic acid bacteria in the yogurt. Let me introduce myself, I am a yeast, because I am a fungus, so I am a little bigger than you, and my body structure is different from yours. It is also a co-distressed brother to be able to pass gastric acid to the intestines. I am very happy to meet you. !” After that, we swam forward along the damp and dark intestines. Slowly, I felt that the oxygen was getting thinner and thinner, so I asked: “Brother Yeast, there is almost no oxygen here. You can live here. Right?” He said with a smile: “My friend, when we have oxygen, our yeast will convert sugar into energy and carbon dioxide. The holes in the fluffy bread are our “masterpiece”. When there is no oxygen, we It converts sugar into energy and alcohol. With this ability, we have a place in human bakery and brewery.”

When the surrounding microbial residents saw us coming, they all looked up and down around us. Suddenly someone in the flora yelled: “Brothers, the master is eating again and is ready to start work.” Then he turned to me and said, “Hello! We are all microbes in the intestines-probiotics that live in symbiosis with humans all year round. Press In terms of classification, I belong to Escherichia coli, which is one of the common bacteria in the intestinal tract. We obtain nutrients from human intestines, and at the same time produce nutrients and maintain intestinal health. But when the owner eats something unclean, it will also Bring some bad egg bacteria, such as Shigella dysentery over there.” It pointed to a bacillus tied up with five flowers next to it. “These bad egg bacteria rob us of nutrients and release toxins. It is it that makes the owner diarrhea.” At this time, another large intestine. Bacillus came over and said, “No, the toxin released by Shigella will cause diarrhea. Be careful, I have to go and help.” As soon as E. coli’s voice fell, the intestinal tract began to move violently, and the yeast brothers and I were shaken. Su, suddenly a bright light appeared in front of me, and I fainted.

Schematic diagram of yeast alcohol fermentation

Lactic acid bacteria is a general term for bacteria that can produce large amounts of lactic acid from fermentable carbohydrates.

According to their morphology, lactic acid bacteria can be divided into five genera: Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium and Pediococcus.

Lactic acid bacteria can promote animal growth, improve gastrointestinal function, help digestion and lower serum cholesterol, control endotoxins, and improve immunity.

Wonderful forms of the three microbial families

Lost City Sewer
“Friend, wake up! We followed the human feces to the sewer.” I was awakened by the yeast brother beside me. The dirty water and excrement made me very uncomfortable. “Brother, it’s so dirty here. Let’s hurry and leave. Maybe we can escape to the sewage treatment plant along the pipeline. It is estimated that it will be much safer there.” Before I finished speaking, he suddenly pulled me and hid behind the garbage, whispering Said: “Be careful, there are phages in front.” I saw a group of densely packed small things burrow out of a broken body of bacteria. It shocked me. Yeast brother said: “Bacteriophages are a branch of the virus family and the nemesis of bacteria. They can inject their core DNA toxins into the bacteria, and then use the bacteria’s body as a raw material to produce more phages, and then swell. The body of the bacteria burrows out, so if you are caught by the phage, you will be unlucky.” Hearing this, I couldn’t help but start to sweat. After the phage was gone, we found that the lysed bacterial carcass was the Yersinia pestis in the sewer. This virus has great lethality to mice and humans. This kind of bacteria usually infects humans through fleas on mice, and then infects humans. The plague is very terrible. The “Black Death” that caused human losses in the past refers to the plague.

We continued to move forward. Sure enough, in the sewage, we found that the Yersinia pestis was continuously released from the dead rats’ carcasses, floating around. I deeply feel that the Yersinia pestis is by no means a good kind. We both speeded up the swimming speed and rushed to the sewage treatment plant.

Phage is a general term for viruses that infect microorganisms such as bacteria, fungi, algae, actinomycetes or spirochetes. Because some of them can cause the lysis of host bacteria, they are called bacteriophages.

Phage shapes are tadpole-shaped, micro-spherical and thin rod-shaped, and are more common in tadpole-shaped. Bacteriophages are composed of nucleic acids and proteins.

Phage can be used to identify and type bacteria, detect and control pathogenic bacteria, and even treat human diseases.

Parting gift of “old bacteria”
After reaching the sewage treatment plant, the toxins in the sewage are removed step by step. I bid farewell to Big Yeast, and plan to see the broader microbial world in the city by myself. “Children!” An elderly bacterium patted us from behind, “I haven’t seen you before, so I must have come from afar. In order to pass on the special abilities I acquired in the sewage plant, Lactobacillus kid, let me come. Teach you a new ability.” It gave me a gene fragment, and after speaking, the old bacteria disappeared. I took a closer look at the gene fragments, it can degrade ammonia nitrogen waste in sewage, and after reading it, I have the ability to degrade ammonia nitrogen.

A few days later, the researchers stood by the pool to take water samples. I was full of curiosity struggling to swim into the bottle and fell asleep under the low temperature of liquid nitrogen, looking forward to a more wonderful journey after waking up. Maybe I don’t know yet, I will return to the sewage treatment plant with this new ability and more brothers and sisters and embark on a new journey of filtering drinking water.

Yersinia pestis
Yersinia pestis belongs to the genus Yersinia. The initial culture was oval. For aerobic and facultative anaerobes, the optimum temperature is 27~28℃. The ability to survive is very strong, it is not easy to die under cold and humid conditions, it can still survive at -30℃, and it can survive at 5-10℃. Plague is a natural foci of a severe infectious disease caused by the bacterium Yersinia pestis, also called the Black Death. According to different modes of transmission, it is divided into bubonic plague, septic plague and pneumonic plague.