Conversely, if the solute concentration of the environment is higher than the solute concentration found inside the cell, the environment is said to be hypertonic. Ultraviolet radiation has been used as a germicide by both industry and medicine for more than a century see. Halophiles- Grow in the presence of salt at conc. The cell collapse and cell membrane pulls away from the cell wall in plants. Whether fatty acids in a membrane are in a liquid or a solid phase affects the fluidity of the membrane, which directly affects its ability to function. Some bacterial cells grow better in acidic or basic environments others may only grow in extremely warm temperatures.
Specific growth factors may also be required such as blood or specific type of protein. Osmosis is powered by the potential energy of a concentration gradient and does not require the expenditure of metabolic energy. Thermal processes often cause undesirable changes in the texture, appearance and nutritional value of foods. Different microorganisms have different minimal or maximal temperature level they can tolerate in their environment. The Lag phase is when the bacterial cell increases in size, the Log phase is when the cells increase in number, the Stationary phase is when cells begin to die off and finally the Decline phase is when the number of dead cells exceeds the number of cells being made.
Medical Microbiology, 23 rd edition. The minimum and maximum temperature of psychrophiles is 0 oC and 20 oC respectively while their optimum temperature is 15 oC. Instead they use organic compounds as a carbon source. Oxygen Concentration The oxygen requirement of an organism relates to the type of metabolism that it is using. These enzymes protect microbes against lethal effects of oxygen products. Temperature In general, the higher the temperature, the more easily microorganisms can grow up to a certain point. Examples of psychrotrophs include Pseudomonas fluorescens and Listeria monocytogenes a major food-pathogen found in diary and meat products.
Psychrophiles have an increased amount of unsaturated and shorter-chain fatty acids. Growth and death rates of microorganisms are greatly influenced by number of environmental factors such as solutes and water acidity, temperature, oxygen requirement, pH, pressure and radiation. They are responsible for spoiling refrigerated foods Psychrotrophic bacteria are of particular concern to the dairy industry. There are some microbes, however, that have evolved to live in the extreme pH environments. Every microbial species has a set of optimal conditions under which it flourishes. The spoilage of refrigerated food takes place because of facultative psychrophiles.
This is a significant step that reiterates the need for a new approach to the old problem of studying environmental extremes through experiments. Knowing the different physical and chemical factors that affect the growth and survival of microbial cells in the environment will help to strengthen efforts geared towards their control, and thus reduce or eliminate their deleterious effects to mankind, animals and the environment. Almost all of the human microflora fall into this category, as well as almost all human pathogens. These archaea survive at pH values of 2. While water molecules are small enough to pass between the phospholipids in the cytoplasmic membrane, their transport can be enhanced by water transporting transport proteins known as aquaporins.
Lactic acid bacteria that ferment milk into yogurt or transform vegetables in pickles thrive at a pH close to 4. For practical purposes, there are three categories of anaerobe: Obligate anaerobes, which are harmed by the presence of oxygen. However, microaerophiles metabolise energy aerobically, and obligate anaerobes metabolise energy anaerobically. The cell: A Molecular Approach. It is the cause of strep throat, rheumatic fever,glomerulonephritis and scarlet fever. Psychrophiles are majorly found in the Antarctic and Arctic regions of the earth and even in snow-prone regions. Environmental pH The pH level of an environment can either help or hurt the growth of microbes.
Each curve has an optimal pH and extreme pH values at which growth is much reduced. Optimum temperature between 25°C and 45°C. At freezing temperatures enzyme activity can stop. Both of these factors are now contributing to more frequent and more extreme fires in recent years. Examples: Thermus aquaticus, Geogemma barossii, etc. A danger inherent in using high temperatures to destroy microbes, is their incomplete destruction through inadequate procedures with a consequent risk of producing pathogens resistant to heat.
The enzyme catalase decomposes hydrogen peroxide into oxygen and water. They typically employ antiporters, which pump protons in and sodium ions out. Organisms such as these produce odoriferous gases in their metabolism, including hydrogen sulfide gas and methane. Each microbe shows characteristic temperature dependence and possesses its own cardinal temperatures i. While water molecules are small enough to pass between the phospholipids in the cytoplasmic membrane, their transport can be enhanced by water transporting transport proteins known as aquaporins. All the species survived weaker radiation doses with little damage, while only the species survived much larger doses.