Gram-negative bacterial flora on the root surface of wheat (Triticum aestivum) grown under different soil conditions

1996 ◽  
Vol 23 (3) ◽  
pp. 273-281
Author(s):  
K. Sato ◽  
J.-Y. Jiang
Keyword(s):  
Triticum Aestivum ◽  
Bacterial Flora ◽  
Root Surface ◽  
Soil Conditions ◽  
Gram Negative

BACTERICIDAL FUNCTION OF HUMAN POLYMORPHONUCLEAR LEUKOCYTES

PEDIATRICS ◽  
1972 ◽  
Vol 50 (2) ◽  
pp. 264-270
Author(s):  
Paul G. Quie
Keyword(s):  
Hydrogen Peroxide ◽  
Chronic Granulomatous Disease ◽  
Polymorphonuclear Leukocytes ◽  
Bacterial Species ◽  
Bacterial Flora ◽  
Granulomatous Disease ◽  
Serum Factors ◽  
Gram Negative ◽  
Increased Risk ◽  
Human Polymorphonuclear Leukocytes

Serum from most normal persons contains specific antibodies which react with common bacterial species preparing their surfaces so that phagocytosis by leukocytes can take place. The Fab part of these antibodies reacts with immunologic specificity with antigens on the surface of bacteria. Another part of the immunoglobulin molecule termed the Fc portion is activated during the attachment of the Fab portion to bacteria and becomes a site for attachment of bacteria to receptors on the surface of phagocytic cells. This activity is greatly amplified by heat-labile serum factors. Normally bacteria are rapidly killed by human polymorphonuclear leukocytes after engulfment occurs. However staphylococci and gram-negative species of bacteria survive in the leukocytes of patients with the syndrome "Chronic Granulomatous Disease of Childhood." These patients have suffered recurrent severe infections with bacterial species that are part of the body's resident bacterial flora. By contrast these patients are not at increased risk to infection from such pyogenic bacterial species as group A streptococci or pneumococci. The leukocytes from patients with chronic granulomatous disease produce little hydrogen peroxide during phagocytosis. Catalase-producing staphylococci and gram-negative bacteria are not killed, but hydrogen peroxide-producing streptococci and pneumococci are killed. A normal metabolic response to phagocytosis as well as release of lysosonial factors are essential for the bactericidal activity of human polymorphonuclear leukocytes.

scholarly journals A survey of trimethoprim resistance in the enteric bacterial flora of farm animals

1979 ◽  
Vol 82 (3) ◽  
pp. 481-488 ◽  
Author(s):  
B. West ◽  
G. White
Keyword(s):  
Great Britain ◽  
Salmonella Typhimurium ◽  
Bacterial Flora ◽  
Enteric Bacteria ◽  
Farm Animals ◽  
Gram Negative ◽  
Resistant Strains ◽  
R Factors

SUMMARYFor 29 months the Veterinary Investigation Centres, covering the whole of Great Britain, forwarded trimethoprim-resistant gram negative enteric bacteria to the Wellcome Research Laboratories. These were examined for degree of resistance, presence and type of R factors. Trimethoprim resistance was found in 0·6 % of the total number of strains examined by the Veterinary Investigation Centres. Trimethoprim R factors were demonstrated in one quarter of the resistant strains, and R factors were found in two strains ofSalmonella typhimurium. It was concluded that while the incidence of trimethoprim resistance revealed by the survey gave no cause for alarm, the detection of resistant strains, and particularly R factors, indicated that the drug should continue to be used only for specific therapeutic purposes.

scholarly journals THE GASTROINTESTINAL EPITHELIUM AND ITS AUTOCHTHONOUS BACTERIAL FLORA

1968 ◽  
Vol 127 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Dwayne C. Savage ◽  
René Dubos ◽  
Russell W. Schaedler
Keyword(s):  
Gastrointestinal Tract ◽  
Bacterial Flora ◽  
Normal Flora ◽  
Culture Methods ◽  
Gram Positive ◽  
Histological Techniques ◽  
Gram Negative ◽  
Mucous Layer ◽  
Histological Sections ◽  
Gram Positive Cocci

Colonization of the gastrointestinal tract by bacteria of the normal flora was followed by bacteriological and special histological techniques in mice from several colonies. These histological techniques were designed to preserve the intimate associations that become established between particular strains of microorganisms and the epithelium of the mucosa of certain areas of the gut. The findings were as follows: 1. The various strains of bacteria of the normal flora became established in the different areas of the guts of infant mice according to a definite time sequence. 2. The first types of bacteria that could be cultured from the gut were lactobacilli and Group N streptococci. Within the first day after birth, these bacteria colonized the entire digestive tract and formed layers on the stratified squamous epithelium of the nonsecreting portion of the stomach and of the distal esophagus. 3. The bacterial types that appeared next were coliforms and enterococci. From about the 9th to the 18th day after birth, these bacteria could be cultured in extremely high numbers from the cecum and the colon. Histological sections of those organs taken during the first 2 or 3 days of that interval revealed microcolonies of Gram-positive cocci in pairs and tiny Gram-negative rods embedded in the mucous layer of the epithelium. The microcolonies were well separated from the mixture of digesta and bacteria that occupied the center of the lumen; they may have consisted of the coliforms and enterococci mentioned above; but this possibility remains to be proved. 4. Histological sections also revealed that, at about the 12th day after birth, long, thin Gram-variable rods with tapering ends were present, side by side, with the small Gram-negative rods and Gram-positive cocci in the mucous layer. By the 15th day after birth, the fusiform bacteria formed thick layers in the mucus, and seemed to be the only bacteria remaining in that location. It has not yet been possible to enumerate these tapered rods by culture methods, but as judged by visual appearances in the histological sections, they seemed to outnumber all other bacteria in the cecum and the colon by a factor of as much as 1000. It must be stressed that these bacterial layers are readily disrupted and even washed away by conventional histological techniques; their discovery was largely due to the use of the special histological techniques described in the text. The bacteriological and histological findings described here constitute further evidence for the hypothesis that symbiotic associations exist between microorganisms and animals, and that a very large percentage of the bacteria in the gastrointestinal tract constitutes a true autochthonous flora. The constant occurrence of several distinct associations of bacteria with the special histological structures of the animal host renders obsolete the notion that the intestine constitutes a chemostat in which the bacterial populations are randomly mixed. For a full understanding of the ecology of the normal microflora, it is necessary to think of body surfaces as distinct microenvironments in which virtually pure cultures of a few species of microorganisms interact with their host and the adjacent microbial populations. Experiments based on this hypothesis are admittedly difficult to design, but on the other hand studies based on the assumption that microorganisms exist as mixtures in the gastrointestinal tract will be only of limited value and may often be misleading.

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