IndexCharacteristics of facultative negative aerobic rodsMethods of feeding calvesResultsOther urease-positive gram-negative isolates from calves MorphologyBiochemical readingDiscussionA facultative aerobe is an organism that produces ATP by aerobic respiration if oxygen is present , but is capable of switching to fermentation or anaerobic respiration in the absence of oxygen. An obligate aerobe, in contrast, cannot produce ATP in the absence of oxygen, and obligate anaerobes die in the presence of oxygen. Some examples of facultative aerobic bacteria are Staphylococcus spp., Streptococcus spp, Escherichia coli, Salmonella, Listeria spp, and Shewanella oneidensis. Some eukaryotes are also facultative aerobes, including fungi such as Saccharomyces cerevisiae and many aquatic invertebrates such as polychaete Nereids (worms). Examples Streptococcus sanguineous streptococcus aralis Facultative aerobes: can grow with or without oxygen because they can metabolize energy aerobically or anaerobically. They gather mostly high up because aerobic respiration generates more ATP than fermentation or anaerobic respiration. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Characteristics of Aerobic Facultative Negative Sticks Bacterial counts on the liquid phase of a fixed-bed anaerobic digester, treating a pre-fermented, deproteinized cheese whey substrate, were conducted on two different media under aerobic and facultative conditions. Average counts of 16.6×10(6) and 26.5×10(6) ml(-1) were obtained on the two media, with the nutritionally poorer of the two providing the average count results. taller. Seventy-five isolates were obtained from both media, incubated aerobically and in anaerobic containers. These isolates and 13 reference strains were phenotypically characterized. Similarities between crops were calculated using the Sokal and Michener similarity coefficient. Organisms were grouped using the unweighted pair group method and the results presented as a simplified dendrogram. be divided into 3 main groups: gram-negative fermentation rods, mainly Enterobacter, Klebsiella and Citrobacter, with Klebsiella as the predominant genus; gram-positive bacteria, mainly enterococci; and nonfermenting Gram-negative rods of the genera Pseudomonas, Alcaligenes, and Acinetobacter. All enterobacteria and enterococci were capable of producing acetic acid, an intermediate of methanogenesis. Some facultative anaerobic Gram-negative rods from calf and sheep rumenSUMMARY: The coliform population in the rumen of twelve calves aged 10 to 105 days was never greater than 106/g and consisted mainly of Escherichia coZi and intermediate types. Only one well-capsulated strain of Aerobacter aerogenes was isolated, whereas such capsulated strains could be easily isolated from the rumen of a starch-fed sheep. An unidentified small catalase-negative Gram-negative rod, which readily produced ammonia from urea, was isolated from the rumen contents of two of the older calves, at a dilution of lo-'. Mann, Masson & Oxford (19544) demonstrated that, although the rumen coliform population of hay-fed adult sheep was numerically quite small, it nevertheless consisted mainly of intestinal-type Escherichia coli rather than Aerobacter aerogenes or A. cloacae, the common saprophytes found on plants and cereals. A. aerogenes in the capsulated form, however, has since been isolated quite easily from the rumen of a starch-fed sheep andconcentrate (see below). It therefore seemed of some interest to study the distribution of coliform types. in the rumen of the young ruminant, in particular of the calf raised with the usual method with milk and initial gruel, from the first attempt to gnaw the straw at the age of 1-2 weeks until the establishment of the complete ruminal microflora after the interruption of milk in the ration . This has now been carried out in conjunction with the aureomycin feeding of calves described by Mann, Masson and Oxford (1954b) which has led to the isolation of lactobacilli from the rumen of only the youngest calves (reported by Mann and Oxford, 1954~). A description is now given of some other unidentified non-coliform Gram-negative rods, also isolated from the rumen of the calf in the same experiment. These appeared to be of possible importance in the functioning of the rumen microflora due to their greater capacity to produce ammonia from urea than that possessed by A. aerogenes or A. cloacae. Calf Feeding Methods This is fully described by Mann et al. ( 1 9 5 4 b ). The calves (twelve in total) were fed initial gruel via bucket. Hay and grass were available after the third week, but fresh milk was discontinued after the sixth week. The three youngest calves examined (10–11 days of age; OC group in Table 1) were slaughtered in March–May 1954 and were thus separated from the main aureomycin feeding experiment of May–August 1953. Isolation of Gram sticks -rumen negatives in pure culture. The bottle counting technique used for the rumen contents of sheep by Heald, Krogh, Mann, Appleby, Masson & Oxford (1953) and for the isolation of rumen lactobacilli by Mann & Oxford (1954a), although suitable for bacteria Gram-positive saccharolytic bacteria Rumen-negative rods cannot be relied upon to provide a true representation of Gram-negative saccharolytic bacteria in the rumen when they are in the minority. It was then replaced by the following method. A sample of the rumen contents (10 g.) taken from the total well-mixed contents of a rumen as soon as possible after slaughter of the calf (i.e. within 2 hours) was placed in a sterile McCartney bottle, diluted with an equal weight of solution sterile saline, gassed with sterile CO and shaken mechanically for 20 minutes. to detach as many bacteria as possible from the plant particles. The mixture was then centrifuged very lightly to break down larger plant particles, and tenfold serial dilutions were prepared from the supernatant in sterile saline. One ml. from each dilution was transferred to a sterile Petri dish and embedded at 45 inches in 15 ml of Wright's nutrient agar containing glucose (0.2%) and crystal violet (0.0005%). This low concentration of crystal violet did not inhibit all Gram-positive bacteria, but allowed the maximum number of Gram-negative bacteria (coliform and non-coliform) to form distinct colonies in 48 hours when the plates were incubated anaerobically at 38 hours. However, all Gram-negative isolates obtained in this study were shown to be facultative anaerobes. They were purified by repeated plating on glucose + peptone + yeast extract + salt agar and kept until required in Robertson's cooked meat medium. Examination of Gram-negative rods. Those that fermented lactose in MacConkey's bile salt medium with acid and gas production and were also catalase-positive, were further studied with standard methods for coliform bacteria. Indole was analyzed with the KOV~CS' reagent and both the O'Meara and Barritt modifications of the Voges-Proskauer test were employed. The production of ammoniafrom urea was tested by the method of Christensen (1946) and also in the more highly buffered medium of Stuart, van Stratum and Rustigian. Results Classification of coliform bacteria isolated from the rumen of calves of various ages from 10 to 105 days; the viable coliform population was usually 10L106/g. contents of the rumen; sometimes much less (102/g. in calf 3A), sometimes apparently zero, for example in calves 1 A, 1 Al, 1 C and 2Al. The thirty-nine coliform isolates are classified in Table 1 according to the scheme used by Wilson et al. (1935, p. 156) for milk coliform bacteria. From the table it will be seen that Escherichia coli I and I1 and the intermediate types, all vp-negative and ME-positive, represented 87% of the total isolates, while Aerobacter aerogenes (VP ​​+ MR - ) represented only 18% and A .cloacae was not found. All A. aerogenes isolates attacked urea weakly and inconsistently. Only one of these isolates (out of five) showed well-marked encapsulation and, unlike the other four isolates, fermented adonitol and inositol. Capsulated strains of Aerobacter aerogenes from the rumen of a sheep fed with concentrate: The sheep with ruminal fistulas in question was fed with the following daily ration: hay (300 g.), concentrates (500 g.) and potato starch (200 g. .). The medium used for the isolation of coliforms from rumen contents was MacConkey agar. Encapsulated isolates of Aerobacter aerogenes could invariably be easily obtained from the rumen contents of the above sheep, usually at a dilution of up to 10. Control experiments with rumen contents of two fistulated sheep fed hay confirmed Mann's conclusion et al. (1954a) that it was not possible to isolate A. aerogenes from this source. Twenty-three encapsulated isolates of A. aerogenes were obtained in total from six separate samples of the rumen contents of starch-fed sheep. All produced markedly mucoid colonies on agar media containing a fermentable carbohydrate and were indole and methyl red negative, nitrate reducing, Voges-Proskauer, citrate, catalase and urease positive. No liquefied gelatins isolated, two only fermented starch, six fermented neither dulcitol nor adonitol, two (the starch fermenters) attacked adonitol but not dulcitol, one attacked dulcitol but not adonitol, and the remaining fourteen fermented both of these alcohols of sugar. Gram-negative isolates from calf humansOf eleven catalase-negative non-coliform isolates, two from the OCl calf rumen attacked urea only weakly, while the remaining nine from much older calves (five from calf 2C and four from calf 3A1 ) gave the typical reaction in Christensen's medium after 18 hours, with incubation at 38'. They, however, did not produce the required lowering of pH, comparable to that of an authentic strain of Proteus vutgaris, in the more highly buffered medium of Stuart et al. (1945); but in this case the growth was very poor. All of these nine urease-positive noncoliform isolates appeared to be very similar and a brief description is attached. Morphology Films made from growth on Wright's nutrient agar showed: Gram-negative rods of small rum rods or coco-bacilli, 0.5-1 ,u . x 0-3-0-5 p., with roughly parallel sides and rounded ends, sometimes in short chains but more often arranged in bundles, difficult to distinguish from aggregations of cocci; Gram-negative, non-motile, non-spore-forming. Growth characteristics. The 24 hours. growth on agar consisted of almost colorless, smooth, transparent, punctate colonies up to 0.8 mm. diameter with full edge and convex elevation. After 7 days the colonies were still small (2 mm in diameter),.