STREPTOCOCCUS OF YOGURT ENHANCED WITH SEVERAL ILLUMINATION TECHNIQUES

ALEJANDRO ARIEL GARCIA ARRIAGA, COACALCO DE BERRIOZABAL , ESTADO DE MEXICO, MEXICO.

BACKGROUND

Bacteria has been in the world for thousandsof million of years and they are an importantpart of our life, they live with us and in us,since they are present in our mouth, our skinour digestive tract, etc. They are also everywhere and it is true that many species ofbacteria cause infections to our bodiesproducing sicknesses, some of them fatal ifuntreated. Nevertheless some are very usefuland are important components in dairyproducts such as cheese, cream, yogurt, andit is precisely this that we are going to seetoday.

Watching bacteria is one of the mostamazing things that we can do with anoptical microscope, since they are very, verysmall, even more than protozoa to whomthey serve as food. Obviously like mostmicroscopic beings they are transparent andfor that reason we have to use methods ofillumination to see them.

Yogurt is the product of milk bacterialfermentation, in this case made by astreptococcus which is a kind of bacterialorganization and morphology in order toclassify since streptococcus species alwayslook like rosary beads. The most commonspecies that produces yogurt is Streptococcustermophilus which is what we are going toobserve in the pictures.

ILLUMINATION TECHNIQUES USED INTHIS PRESENTATION.

I used here several methods illumination,and some of the functions that my camerahas such as the negative, colour scale and thegray scale, allows us to appreciate perfectlythe sample.

DARK FIELD

Dark field microscopy which represents abeautiful method of illumination, is similar asif we were looking at the sky in a clear nightwith tons of stars shining. It is easy toproduce even when you do not have a darkfield microscope. You can use the samecondenser of a bright field one to produce it,because the principle of dark field isextremely simple. The only thing that youhave to do is to block the passing of the lightin the center of the condenser or in thesource of light of your microscope with astop. For that you can use a lot of things, forexample a small coin, a small circle of blackcardboard or black plastic, i.e. somethingopaque. The rule is that the size of the stopmust be greater than the numerical apertureof the objective, so the light that reachesyour sample is the one that passes aroundthe stop. It is amazing isn´t it? With thissimple procedure you can observe tons ofmicroscopic things.

OBLIQUE ILLUMINATION.

Oblique illumination is another beautifulform of illuminating a sample in themicroscope. It is another one easy to do andthe only thing that you need is to cut a blackcircle made of black cardboard, black plastic,etc., that fits perfectly the filter tray, or thesource of light of your microscope. To thatcircle you have to cut a small opening in oneextreme of the circle’s diameter, which canbe any form you want (generally it is used asa small circle), to allow light to pass out ofthe center. With this you will enhancecontrast in the sample with a kind of threedimensional relief and of most use with highmagnification.

In this we use circular oblique illuminationwhich is a kind of oblique illumination withthe difference that this is made of a centralstop that blocks light as in dark field plusseveral light and dark circles. Circular obliqueillumination is widely discussed in the articlesin the MICSCAPE LIBRARY by Paul James fromthe UK.

My filter for circular oblique illumination:

DIY-DIC.

This is a kind of filter for the obliqueillumination technique that uses a blackcircle with a small hole in the center, which iscovered originally with a blue translucentpatch, and at one extreme of the black circle,a half moon shaped opening. I particularlyhave used other color centers like the redone that I used here in this presentation.

The filters that I used in this presentation:

NEGATIVE FORM OF LIGHTING.

Modern cameras have a lot of functions suchas white balance, color and gray scales, andin the case of mine also has a negativelighting effect, which enhances a picturechanging the color to a negative one, forexample black is seen white, white is seeingblack a so on, now I combine in thispresentation both the color and the negativeeffects of the camera with the dark fieldcondenser and with the bright field one witha filter on the filter tray or without it.

RESULTS

Here are the samples of a drop of yogurtdiluted in some purified water. I have kept inrefrigeration this yogurt for several months inmy refrigerator, that is the reason you canappreciate in the sample apart of thestreptococcus that you can see like smallbead-like chains. The ovals or circles are astrain of fungi that grew in the yogurtcontainer and that is also diluted in thesample. Diplococcus are also seen in thepictures.

Streptococcus 40x 5MP darkfield with enhanced contrast 100, colour temperature 6503K, tint 1000.

Streptococcus 40x 5MP DIY-DIC blue center.

Streptococcus 40x 5MP DIY-DIC red center.

Streptococcus 40x 5MP DIY-DIC red center negative effect of the camera.

Streptococcus 40x 5MP circular oblique illumination

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Streptococcus 40x 5MP circular oblique illumination negative effect of the camera.

Streptococcus 40x 5MP gray scale plus negative effect of the camera.

Streptococcus 40x 5MP dark field condenser plus gray scale plus negative effect of the camera.

Streptococcus 40x 5MP dark field condenser plus color scale plus negative effect of thecamera

CONCLUSION:

As you can see, the enhancement of amicroscopic sample can be achieved inseveral ways, the only thing that you haveto do is to use the resources you have athand. If you still do not have a camera, justtry the observation with the suggestions

that are presented in the MICSCAPElibrary. I tried them before having mycamera, and I had a lot of fun. Now that Ihave my camera I have taken advantage ofthe functions it has and believe me it givesme more fun while observing thismarvelous miniature world.

Email author: doctor2408 AT yahoo DOT com DOT mx

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Presented in the March – April 2015 issue of Micscape Magazine.

www.micscape.org