The science and practice of cheese-making : a treatise on the manufacture of American Cheddar cheese and other varieties : intended as a text-book for the use of dairy teachers and students in classroom and workroom ... . F BALL-SHAPED (coccus) BAC-TERIA (Rogers) (2) Method of grozvth and reproduction.—Theymultiply in number, or reproduce, by simple division;that is, when a cell grows in size, it increases morein one direction, so as to result in lengthening outslightly, and a partition forms across the cell, thusproducing two new cells in place of the old one; andthen each of these subdivides
The science and practice of cheese-making : a treatise on the manufacture of American Cheddar cheese and other varieties : intended as a text-book for the use of dairy teachers and students in classroom and workroom ... . F BALL-SHAPED (coccus) BAC-TERIA (Rogers) (2) Method of grozvth and reproduction.—Theymultiply in number, or reproduce, by simple division;that is, when a cell grows in size, it increases morein one direction, so as to result in lengthening outslightly, and a partition forms across the cell, thusproducing two new cells in place of the old one; andthen each of these subdivides again and so on con-tinuously. Some kinds of bacteria form spores inthe cells; these are to bacteria what seeds are to 2S^ SCIENCE AND PRACTICE OF CHEESE-MAKING higher plants. Spores are not so easily killed by heatas are bacteria. Under favorable conditions, therapidity of growth of bacteria is remarkable. Thus,in some cases, one cell divides into two cells in 20minutes; if this rate were kept up for 24 hours, theone cell would multiply into several millions. (3) Food requirements of bacteria.—Bacteria re-quire as food for satisfactory growth compounds con-taining nitrogen, carbon, hydrogen and, in addition,. FIG. 41—ROD-SHAPED BAC-TERIA (bacillus). CLEARAREAS IN SOME ARE SPORES. (Rogers) FIG. 42—B A C T E R I A WITHHAIR-LIKE ORGANS, WHICHTHEY USE IN MOVINGTHEMSELVES ABOUT IN LIQUIDS (Rogers) small amounts of inorganic or mineral matter. Thesugar, casein, albumin and salts in milk and itsproducts furnish a supply of food very readilyutilized by bacteria. (4) Temperature.—The bacteria commonly pres-ent in milk grow between the limits of 40° and 110°F., the miost favorable limits being between 80° and95° F. Many bacteria are killed between 130° and MICRO-ORGANISMS AND ENZYMS 289 140° F., when exposed to this heat for ten minutes,and most of them are destroyed at 185° F. Many-spores are killed at temperatures only above 212°F., and even then require heating one
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Keywords: ., bookcentury1900, bookdecade1920, bookidsciencepract, bookyear1921
