- M. luteus is an obligate aerobe (Medical Laboratories). The positive catalase result lines up with M. luteus (Public Health England). The colony morphology of being yellow, shiny and smooth line up perfectly with M. luteus (Public Health England). The antibiotic resistance test showed only minor resistance to the antibiotic Oxacillin, which is likely due to a chance inheritance in the population or complete chance because of the weak strength.
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Mar 27, 2020 · What Is the Morphology of Micrococcus Luteus? Micrococcus luteus is a spherical bacteria of between 0.5 and 3.5 millimeters in length that grows in aerobic environments and forms yellow colonies when grown on agar plates. Micrococcus luteus is typically Gram-positive, though it can sometimes be Gram-variable depending on the strain.
Intro: Microbes are everywhere, even in the most extreme environments and conditions. They can be found in boiling hot springs; they can be found in frigid waters in the artic. They can even survive in conditions that have very little of even no oxygen, using glycolysis and alternative electron acceptors to create ATP. With this almost universal range of survivable living conditions that microbes can live in (particularly bacteria), it would be reasonable to assume that there would be at least one variety living in such a nice, wet, and aerated place as my shower drain. Therefore I used this as my location to take my environmental sample from. I would hypothesise that because we clean our shower regularly, that most of the bacterium un the shower drain would come from people in my family taking a shower, and mostly be from the skin. Organisms commonly found on the body include Micrococcus, Staphylococcus, and Corynebacterium species (Dermnet New Zeland). These residential skin organisms are also fairly ubiquitous in the environment. We were aiming to isolate a bacterium from this initial environmental sample by using repeated quadrant streaks to isolate single species colonies, therefore producing a pure culture that we could do a multitude of tests on which include Gram staining, genetic analysis and antibiotic testing along with many other tests. Based on the place of origin of the bacterium that I isolated, I hypothesize that it will either be one of the above bacterium or a similar water loving organism, likely one that also forms a biofilm. I also hypothesize that it will be an aerobic organism, given that I found it in a well aerated environment and it has survived until I cultured it. When looking back after culturing the isolate, these hypothesies were supported by several of the tests, and served as a good tool to steer me towards what the isolate may be.
Results: Regarding the gram stain test, my isolate was gram variable, I ensured that the strain was fresh so that the age of the culture was the same throughout the test. Most of the bacterium in the gram stains were gram negative, but a significant amount, about twenty percent, showed up as gram positive. The colonies are a pale, translucent yellow, and are shiny when looked at in the light. They are fairly small as well, usually about a millimeter in diameter and of a normal height. Under the microscope they are round cells. When performing tests for physiological traits, the results were limited. When using a fluid thyoglycollate test it resulted in the isolate being a strict aerobe, with all of the bacterium being at the top of the medium where it is oxygenic. The oxidase test was negative, as the strip did not change color at all, where it would have turned purple if it was positive. The catalase test did return positive by bubbling, indicating that it does have the ability to break down the radical hydrogen peroxide into diatomic oxygen and hydrogen. Finally, when looking at the API 20E strip none of the results returned positive despite the culture being active and fresh from being streaked recently. When looking back at all the data, it is fairly likely that the isolate is Micrococcus luteus, especially when looking at the fluid thyoglycate test, the colony morphology, and the antibiotic susceptibility. The tests that did not agree were most likely from not having an active colony used in the experiment, such as the oxidase test being negative or the API 20 E test strip showing that the isolate did not reduce nitrate, which it does, referencing Medical Laboratories. I also had to do the thyoglycate test 3 times to get a conclusive result, further making me skeptical of how active the culture was during the physical tests during week 6, which is where almost all of the inconsistencies arose.
When looking at the genetic tests, most of the identified strains in the Korona test are Micrococcus luteus. The identified reads only made up a total of twenty seven percent of the total reads, but the majority of those reads were for M. luteus. The confidence on that reading is decently confident, evidenced by the blue coloring. The results of this analysis are shown in table 1.
Table 1: Graph from Korona showing the percent reads of each organism, and to which taxonomic level.
Table 2: Graph of the genomic reads by taxonomic level using Korona. M. luteus is the majority of reads on the species level.
When looking at the antibiotic test results, the isolate is resistant to none of the applied antibiotics, and is only lightly to intermediately resistant to oxacillin. The Gentamicin, Cefoperazone, Vancomycin, Tobramycin, Amikacin, Trimethoprim, and Cefazdin antibiotics showed obvious susceptibility, with most of them having enormous rings of 50 to 52 millimeters while the threshold for resistance is only 15 millimeters. Of those only Vancomycin was closer than 50 millimeters, being 38 millimeters.
Many of the tests did line up with M. luteus though, such as the fluid thyoglycate test, which showed that it was an obligate aerobe. M. luteus is an obligate aerobe (Medical Laboratories). The positive catalase result lines up with M. luteus (Public Health England). The colony morphology of being yellow, shiny and smooth line up perfectly with M. luteus (Public Health England). The antibiotic resistance test showed only minor resistance to the antibiotic Oxacillin, which is likely due to a chance inheritance in the population or complete chance because of the weak strength. The organism itself is susceptible to almost all drugs, with a few strains being resistant to nitrofurantoin, macrolides and lincomycin (Public Health Canada). This lines up with M. luteus resistances from the tests.
The Micrococcus genus is known to be found on dust particles, in water, on skin and skin glands in vertebrates, and some species can be found in milk. They are fairly ubiquitous in the environment, and are small (0.5 to 3.5 micrometers in diameter) and non-motile. This fits well with where I sampled my bacterium from, as a shower drain is a place where both dust and water would accumulate, along with residues of skin glands from showering. It is an opportunistic pathogen, only pathogenic enough to cause disease in weakened immune systems (Medical Laboratories). The colony morphology is the same as well, being round, shiny, and sort of flat (Medical Laboratories).
If I were to continue researching this isolate, I would redo the API 20 E test strip with a fresh, active culture to ensure that it can reduce nitrate, and also the oxidase test to ensure that it does have cytochrome c oxidase present, which it should according to Public Health England. Further tests that I would do would be testing how much heat resistance it has, the density of a broth suspended sample using a dilution series, test for more antibiotic resistances, and how well it can grow in antibacterial mediums and mediums of different pH levels.
The membranes of M. luteus are rich in enzymes that catalyze the synthesis of prenyl pyrophosphates at chain lengths between 15 to 45 carbon atoms [Saito and Ogura, 1981]. A number of interesting biological issues are also inherent in the study of M. luteus , including dormancy without spore formation, resuscitation from dormancy, and the ...
2406. Micrococcus luteus is a Gram-positive, to Gram-variable, nonmotile, coccus, tetrad-arranging, pigmented, saprotrophic bacterium that belongs to the family Micrococcaceae. It is urease and catalase positive. Micrococcus luteus is a Gram-positive, spherical, saprotrophic bacterium . An obligate aerobe, M. ….
Micrococcus luteus is a Gram-positive, to Gram-variable, nonmotile, coccus, tetrad-arranging, pigmented, saprotrophic bacterium that belongs to the family Micrococcaceae. It is urease and catalase positive. An obligate aerobe, M. luteus is found in soil, dust, water and air, and as part of the normal microbiota of the mammalian skin.