Charles is a retired bus driver who developed type 2 diabetes over 10 years ago. Since his retirement, his lifestyle has become very sedentary and he has put on a substantial amount of weight. Because the sore did not bother him much, Charles figured it could not be serious until his daughter noticed a purplish discoloration spreading on the skin and oozing Figure 4.
When he was finally seen by his physician, Charles was rushed to the operating room. His open sore, or ulcer, is the result of a diabetic foot. The concern here is that gas gangrene may have taken hold in the dead tissue. The most likely agent of gas gangrene is Clostridium perfringens , an endospore-forming, gram-positive bacterium. It is an obligate anaerobe that grows in tissue devoid of oxygen. Since dead tissue is no longer supplied with oxygen by the circulatory system, the dead tissue provides pockets of ideal environment for the growth of C.
The wound will have to be surgically debrided debridement refers to the removal of dead and infected tissue and a sample sent for microbiological lab analysis, but Charles will not have to have his foot amputated. Many diabetic patients are not so lucky.
In , nearly 70, diabetic patients in the United States lost a foot or limb to amputation, according to statistics from the Centers for Disease Control and Prevention. Aerobic respiration constantly generates reactive oxygen species ROS , byproducts that must be detoxified.
Even organisms that do not use aerobic respiration need some way to break down some of the ROS that may form from atmospheric oxygen. Three main enzymes break down those toxic byproducts: superoxide dismutase, peroxidase, and catalase. Each one catalyzes a different reaction. Reactions of type seen in Reaction 1 are catalyzed by peroxidases. In these reactions, an electron donor reduced compound; e.
The enzymes play an important role by limiting the damage caused by peroxidation of membrane lipids. Reaction 2 is mediated by the enzyme superoxide dismutase SOD and breaks down the powerful superoxide anions generated by aerobic metabolism:. Figure 5. The catalase test detects the presence of the enzyme catalase by noting whether bubbles are released when hydrogen peroxide is added to a culture sample.
Compare the positive result right with the negative result left. Obligate anaerobes usually lack all three enzymes. Aerotolerant anaerobes do have SOD but no catalase. Reaction 3, shown occurring in Figure 5, is the basis of a useful and rapid test to distinguish streptococci, which are aerotolerant and do not possess catalase, from staphylococci, which are facultative anaerobes.
Bacteria that grow best in a higher concentration of CO 2 and a lower concentration of oxygen than present in the atmosphere are called capnophiles. One common approach to grow capnophiles is to use a candle jar. A candle jar consists of a jar with a tight-fitting lid that can accommodate the cultures and a candle. After the cultures are added to the jar, the candle is lit and the lid closed. As the candle burns, it consumes most of the oxygen present and releases CO 2.
The health-care provider who saw Nataliya was concerned primarily because of her pregnancy. Her condition enhances the risk for infections and makes her more vulnerable to those infections. The immune system is downregulated during pregnancy, and pathogens that cross the placenta can be very dangerous for the fetus. Blood is considered sterile; therefore, competing microorganisms are not expected in the medium.
Small grayish colonies surrounded by a clear zone emerge. Such colonies are typical of Listeria and other pathogens such as streptococci; the clear zone surrounding the colonies indicates complete lysis of blood in the medium, referred to as beta-hemolysis Figure 6.
When tested for the presence of catalase, the colonies give a positive response, eliminating Streptococcus as a possible cause.
Furthermore, a Gram stain shows short gram-positive bacilli. Cells from a broth culture grown at room temperature displayed the tumbling motility characteristic of Listeria Figure 6. Figure 6. An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion?
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Flint, D. Obligate anaerobes may use fermentation or anaerobic respiration. In the presence of oxygen, facultative anaerobes use aerobic respiration ; without oxygen some of them ferment, some use anaerobic respiration. Aerotolerant organisms are strictly fermentative. Microaerophiles carry out aerobic respiration, and some of them can also do anaerobic respiration. Fermentative anaerobic organisms mostly use the lactic acid fermentation pathway:.
Plants and fungi e. Anaerobic bacteria and archaea use these and many other fermentative pathways, e. Some anaerobic bacteria produce toxins e. Obligate strict anaerobes die in presence of oxygen due to the absence of the enzymes superoxide dismutase and catalase which would convert the lethal superoxide formed in their cells due to the presence of oxygen.
Instead of oxygen, obligate anaerobes use alternate electron acceptors for respiration such as sulfate, nitrate , iron , manganese , mercury, and carbon monoxide. The energey yield of these repiratory processes is less than oxygen respiration, and not all of these electron acceptors are created equally. Anaerobic organism en Espanol. Anaerobic organism en Francais. Anaerobic organism in the Marketplace. Patents on Anaerobic organism. List of terms related to Anaerobic organism.
Editor-In-Chief: C. Michael Gibson, M. An anaerobic organism is any organism that does not require oxygen for growth and even dies in its presence. Microaerophiles are organisms that may use oxygen, but only at low concentrations low micromolar range ; their growth is inhibited by normal oxygen concentrations approximately micromolar.
Nanaerobes are organisms that cannot grow in the presence of micromolar concentrations of oxygen, but can grow with and benefit from nanomolar concentrations of oxygen. Obligate anaerobes may use fermentation or anaerobic respiration. In the presence of oxygen, facultative anaerobes use aerobic respiration ; without oxygen some of them ferment, some use anaerobic respiration. Aerotolerant organisms are strictly fermentative.
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