Halophiles (Halophiles), also known as Vibrio parahaemolyticus, are a type of ancient bacteria that live in high-salinity environments.
The classification of halophilic archaea is divided into one family (halophilic bacteria) and six genera: halophilus, halophilus, halophilic genus, halophilus, halophilus, halophilus Alkalophilus. Usually live in 10% to 30% salt solution. Among the halophilic bacteria, some people also found an archaea with a square shape. Salted food is often eaten in our daily life is also an ideal place to live. Marine fish, jellyfish, sea crabs, sea shells and other marine products, as well as less salty pickles, salted eggs, pickled fish, cured meat and the like, once they are contaminated with halophilic bacteria, they will multiply in large numbers at an alarming rate. Experiments show that the fungus likes the environment with a salt content of 2% to 4%, and it will grow in a high salt concentration of 5% to 6% or a low salt concentration rich in nutrients. Especially in summer with suitable temperature, 10 halophilic bacteria will produce millions of offspring after 3-4 hours. This is a terrible astronomical figure, but the human eye and other sensory organs are difficult to detect.
Adaptation mechanism
Na + dependencies
The halophilic bacteria must survive in a high-salt environment. Na + plays a particularly important role in maintaining the structure and function of cell membranes and cell walls. Na + interacts specifically with cell membrane components to enhance the mechanical strength of the membrane, which is beneficial to maintain the structure of the cell membrane and plays an important role in preventing the lysis of halophilic bacteria. In terms of the function of the cell membrane, Na + must be present in the active transport system of amino acids and sugars in halophilic bacteria, and Na + plays a role as an essential factor in the respiratory response of productivity. Experiments prove that the absorption of amino acids is driven indirectly by light, and an amino acid-Na + pump transport system is used to carry amino acids. Na + is bound to the outer surface of the halophilic cell wall and plays an important role in maintaining cell integrity. The cell wall of the halophilic bacterium replaces the traditional peptidoglycan with a glycoprotein. This glycoprotein contains high amounts of acidic amino acids (such as aspartic acid and glutamic acid), forming a negatively charged region, attracting positively charged Na +, and maintaining Cell wall stability prevents cells from being lysed. "Excess" acidic amino acid residues form a negative electrical shield on the surface of the protein, promoting the stability of the protein in a high salt environment.
Salt adaptation characteristics of enzymes
The halophilic enzyme is active only at high salt concentration. After salt removal, the halophilic enzyme is inactivated. Most of the halophilic enzyme is denatured and inactivated at low salt concentration (1.0mol / L NaCl and KCl). The salt was slowly added back and found to restore enzyme activity. According to the dependence relationship between halophilic enzymes and salt, it can be divided into three categories: the first category is that when no salt is added, the enzyme activity is the highest, and the addition of salt is inhibited. There may be some protective mechanism in this type of halophilic bacteria, and high concentration of K + may act as a protective factor against salt inhibition. The second type is that there is a certain activity when no salt is added, and the enzyme activity is further enhanced when salt is added. The optimal salt concentration is lower than the intracellular ion concentration. Excessive salt concentration will inhibit the enzyme activity, and the third type enzyme is not added Salt shows almost no activity, and the enzyme is strongly activated by the action of salt.
Plasma membrane / pigment / proton pump action
Halophilic bacteria have abnormal membranes. There is an S monolayer with hexagonal arrangement of subunits outside the cell membrane of halophilic bacteria. This so-called 'S monolayer' is composed of sulfonated glycoprotein. Due to the presence of sulfonic acid groups, the S layer is negatively charged, so the composition The glycoproteins of the subunits are shielded and remain stable in high salt environments.
Restricted ventilation, that is, light culture under low oxygen pressure or anaerobic conditions, extreme halophilic bacteria produce red-purple cells. The cell membrane of this cell has purple membrane patch tissue, accounting for about 50% of the whole membrane, by 25 % Lipid and 75% protein. Four special pigment proteins with different functions have been discovered, namely retinal proteins, namely, cell rhodopsin (bR), chlororhodopsin (hR), photosensitive rhodopsin I (SRI) and photosensitive rhodopsin II (SRII), the most thorough research on bR of Halobacterium halobacterium, the trimer composed of three bR molecules can form a rigid two-dimensional hexagonal stable characteristic structure on the cell membrane, namely the purple membrane. The bacteriorhodopsin or rhodopsin contained in the purple membrane is composed of 1: 1 combination of bacteriopsin and carotenoid pigment. The bacteriorhodopsin of halophilic bacteria can strongly absorb the green spectral region at 570nm. The visual chromophore (chromophore) of bacteriorhodopsin usually exists on the inside of the membrane in a full-trans structure, which can be excited and As the light absorption is temporarily converted to the cis state, the result of this transformation is to transfer the H + proton to the outside of the membrane. As the bacteriorhodopsin molecule relaxes and absorbs protons in the cytoplasm during darkness, the cis state changes again. Into a more stable all-trans isomer, again the light absorption is excited again, transfer H +, and so cycle, forming a H + proton gradient difference on the plasma membrane, that is, the proton pump (H + pump), which generates an electrochemical potential, bacteria The body uses this electrochemical potential to synthesize ATP under the catalysis of ATPase to store the energy needed for life activities for the bacteria.
Poisoning
After eating food contaminated with halophilic bacteria, it usually takes 6-20 hours, short 1-3 hours, and long 80 hours before food poisoning occurs-acute gastroenteritis. The patient had abdominal pain and diarrhea first, followed by nausea and vomiting; the abdominal pain presented paroxysmal colic. The diarrhea stool was a meat washing or blood sample with pus or mucus, which would be mistaken for dysentery. In addition, fever, dehydration, acidosis, shock, confusion, and other poisoning symptoms may occur. However, after proper symptomatic treatment, the patient will heal in two or three days without risk or sequelae.
Halophilic food poisoning often has a collective tendency. Because most of the contaminated foods are raw vegetables and cooked foods that are produced in large quantities, and they are cheap and attractive fresh goods. For example, when making noodles with shrimps and crabs during a meal, the outside is crispy and tender inside, and the halophilic bacteria are not killed. Instead, they are wrapped in them to provide excellent environmental conditions. They are left for a long time and suffer after eating. Another situation is that coastal residents like to eat raw small aquatic products, such as "drunk crabs" and "shrimps". Some people may chew on a crab foot or eat a shrimp. The rare customers are often fooled by new taste.
Food poisoning of halophilic bacteria focuses on prevention, and prevention is not difficult. For the bacteria to be salty, let's do the opposite. When eating seafood or pickled foods, first soak them in fresh water and rinse them clean, especially for jellyfish skin and jellyfish heads for raw food. Use cold water for a few more times. Halophilic bacteria also have fatal weaknesses that are afraid of heat and acid, so when cooking fish, meat and other dishes, or when marinating raw products and mixing cold raisins, put onions, ginger, garlic, vinegar and other condiments; The cold mixed raisins are ready-to-eat. The purchased cooked food should be steamed for a while, including the cooked food taken out of the refrigerator.
The Plastic Mulch Film is used to enhance farm produce growth, yield and also the quality. It could prevent the crops contacting with the ground to reduce risk of rotting. Produced with high quality resins , it can endure puncture marks and resist sun light, control weed growth by lowering light transmission to the soil.
Agricultural Mulch Film, Much Film Roll, Biodegradable Mulch Film, Plastic Mulch Film, Plastic Mulch Biodegradable, Black Plastic Mulching Film
BILLION PLASTIC MANUFACTURING CO.,LTD, JIANGMEN , https://www.billion-plastics.com