Observation of microorganisms Microorganisms can only be observed using a microscope. Light microscopes use light as a medium to transmit images to our eyes. Light microscopes have been invented a long time ago, and have gone through various improvisations. Microscopes allow small objects to be seen through increased resolution or resolving power and contrast. Resolution or resolving power is the ability of a microscope lens system to separate two adjacent points on a specimen or object. The greater the resolution, the sharper the image you get. Meanwhile, contrast is the difference in intensity of observation between different parts of the image. Contrast can be increased by staining and adjusting the microscope settings. A microscope consists of lenses arranged in such a way that a magnified image of the specimen can be seen by the observer.There are several types of microscopes. The differences between microscopes are:the electromagnetic wavelength used to produce the image, the condition of the lens and lens settings, the method used to view the image, and the function of the microscope itself. Some types of microscopes include: a. A light microscope is a microscope that uses visible light as a light source for observing specimens. A bright field microscope is a light microscope that is commonly used to observe microorganisms. When observing with this microscope, the background will appear bright. b. A dark field microscope is used to observe microorganisms that cannot be observed with a bright field microscope. This microscope uses a special condenser with a dark background so that microorganisms will appear white on a dark background. c. Luminescent (fluorescent) microscopes use ultraviolet light as a light source. Microorganisms are colored with special dyes and will appear to fluoresce under the microorganisms on a dark background. d. Phase contrast microscopes are used to observe the internal structure of microorganisms with Xrays and are useful for adding contrast when observing transparent specimens. Confocal microscopy allows three-dimensional views of cells or very thin slices. e. Electron microscopes are used to observe objects smaller than 0.2 µm, for example viruses and cell structures. Electron microscopes do not use light or ultraviolet light, but instead use electron beams that have very short wavelengths as a lighting source. There are two types of electron microscopes, namely transmission electron microscopes (TEM) which produce two-dimensional images and scanning electron microscopes (SEM) which produce three-dimensional images. • Microorganism staining Most microorganisms are colorless, so to be able to observe them under a light microscope, it is necessary to stain the microorganisms with certain dyes. Microorganism staining is basically a procedure of coloring microorganisms with a dye that can highlight certain structures of the microorganism that you want to observe. Before microorganisms can be colored, they must first be fixed so that they bind (stick) to the glass object(microscope slides). Without fixation, applying color to the microorganisms followed by the procedure of washing the dye with running water will cause the microorganisms to be washed away. There are three types of coloring, namely simple coloring (simple stain), differential staining (differential staining), and special coloring (special stain). In simple staining, only one type of dye is used and the aim is to color all the cells of the microorganism so that the cellular shape and basic structure can be seen. Chemicals that are added to the dye solution are called enhancers (mordant), an example of a simple dye iscarbol fuchinand safranin. Differential staining uses more than one dye and has a different reaction for each bacteria, so it is used to differentiate bacteria. Differential dyes that are often used areGram staining, which was created by Hans Christian Gram in 1884. This stain is able to distinguish two large groups of bacteria, namely Gram positive and Gram negative. • Microorganisms for human life Microorganisms are found everywhere and their interactions with fellow microorganisms or other organisms can be safe and beneficial or detrimental. Microorganisms tend to be associated with disease, infection or decay. However, most microorganisms contribute to the balance of the environmental ecosystem, especially to human welfare. The beneficial role of microorganisms for human welfare, including: a.Control plant pests. Plant pest control using natural enemies of plant pests continues to be developed in order to reduce the negative impact of pesticide use. For example, the use of Bacillus thuringiensis bacteria to control Crocidolomia binotalis which is a pest of cabbage plants; b.Industry and mining. Development of degradable polymers to overcome the problem of environmental pollution caused by plastic waste that is difficult to decompose. For example, the use of Alcaligenes euthropus bacteria as a producer of poly-3-hydroxy alkanoate (PHA) and poly-β-hydroxy butyrate (PHB) which are raw materials for making plastic that are easy to break down. The cellulose enzyme used in the paper industry is produced by Trichoderma viridae. c.Food. One of the bacteria that is useful in the food sector is Lactobacillus bulgarius which is used to make yoghurt. Utilization of Streptococcus lactis and Streptococcus cremoris bacteria in making cheese and butter. d.Health. Several types of microorganisms such as Pseudomonas and Propionibacterium produce vitamin B12 (cobalamin); the fermentation process of the Ashbya gossypii fungus produces vitamin B2 (riboflavin); The manufacture of synthetic antibiotics and vaccines is also the result of the use of microorganisms.