{"id":6679,"date":"2026-11-02T15:44:37","date_gmt":"2026-11-02T06:44:37","guid":{"rendered":"https:\/\/cm-plus.co.jp\/en\/?post_type=column&p=6679"},"modified":"2026-11-02T15:44:37","modified_gmt":"2026-11-02T06:44:37","slug":"2026_1102","status":"publish","type":"column","link":"https:\/\/cm-plus.co.jp\/en\/column\/gmp\/2026_1102\/","title":{"rendered":"Fundamentals of Microbiology [Part 7]"},"content":{"rendered":"

\"\"
\nWhat Are Bacteria 2-2<\/strong><\/p>\n

Bacteria proliferate by division when the surrounding environment such as temperature, nutrients, oxygen, or osmotic pressure is suitable for the bacteria. This is where one bacterium becomes two, two become four, four become eight, eight become sixteen, and so on, doubling in number. The growth rate varies depending on the type of bacteria and surrounding environmental conditions, but for fast-growing bacteria such as Escherichia coli under optimal conditions, the time required for one division is said to be about 20 minutes. The time required for one division is called generation time. In this way, Escherichia coli can divide once every 20 minutes under optimal conditions, that is, three times per hour. If division continues at this rate, it will be as shown below.<\/p>\n

\"\"<\/p>\n

So if growth continues at this rate, how many viable bacteria will there be after one day? One day = 24 hours = 3 \u00d7 24 = 72 (generations). So putting 72 into n, the calculation is 2\u2077\u00b2<\/sup> = 4.7 \u00d7 10\u00b2\u00b9<\/sup>, an astronomical number.<\/p>\n

When this bacterial growth is plotted on a graph, it is as shown in Figure 1. The left side uses a normal scale, while the right side uses a logarithmic scale for the vertical axis.<\/p>\n

\"\"Figure 1 Microbial Growth<\/strong><\/p>\n

Since microorganisms (bacteria) proliferate by binary fission, if the surrounding environment and nutritional status are suitable for the microorganisms, they can reach an enormous number in a short time. However, in reality, when the number of viable bacteria in the medium reaches about 109<\/sup> to 1010<\/sup> \/ml (1 billion to 10 billion per 1 ml), the growth rate slows down due to depletion of available nutrients, pH changes due to accumulation of metabolic products, etc., and eventually stops, leading to death. The extent of proliferation varies depending on the type of microorganism and the surrounding environment such as nutrients, but it does not continue to proliferate indefinitely.<\/p>\n

\"\"Figure 2 Example of a Microbial Growth Curve<\/strong><\/p>\n

Examples of things with a high number of bacteria in nature include dental plaque (plaque, a slimy and rough substance attached to the surface of teeth) or feces. Dental plaque contains about 600 types of bacteria, and it is said that there are about 100 to 200 million bacteria per 1 mg of plaque.<\/p>\n

How to Express the Number of Microorganisms<\/strong>
\nIn microbiology, large numbers such as 1 million or 100 million, and conversely small numbers such as one-millionth, frequently appear. In such cases, it is easier to understand by considering “how many orders of magnitude” a number has rather than its absolute count. Therefore, in the microbial world, numbers are often expressed in the form of 10\u02e3 (10 to the power of X). For example:
\n\u30fb300 million = 300,000,000 = 3\u00d7108<\/sup> (3 multiplied by 10 to the 8th power)
\n\u30fbOne-millionth = 1\/1,000,000 = 1\/106<\/sup> = 10-6<\/sup> (10 to the negative 6th power)
\nFurthermore, when using common logarithmic notation, log 108<\/sup> = 8. For this reason, the vertical axis of graphs such as microbial death curves is sometimes presented in logarithmic (log) scale.
\nIn addition, when describing the number of microorganisms, an exact count is meaningless. Therefore, it is common practice to express numbers with two significant figures, for example: 2,315,652 \u2248 2.3 million = 2.3 \u00d7 106<\/sup>.<\/div>\n

1 mg of plaque.<\/p>\n

\n

Author<\/strong><\/p>\n

\n
\"\"<\/div>\n
Tatsuo Furuya<\/a>
\nSenior Consultant, GMP Platform, CM Plus Corporation
\nAfter working in sterilization management, microbiology, and quality assurance at Johnson & Johnson, Creative Medic, and Boston Scientific, he joined CM Plus, Inc. in 2013.
\nWhile working for the medical device manufacturer above, he participated in the Health and Welfare Science Research Group and various sterilization-related committees as a specialist in ethylene oxide sterilization.<\/div>\n<\/div>\n

About GMP Platform<\/strong> (<\/span>https:\/\/www.gmp-platform.com\/<\/a><\/span>)<\/span><\/p>\n

\n
\"\"<\/div>\n
GMP Platform is a free GMP-related information portal established in 2012 and operated by CM Plus Corporation. Built on CM Plus\u2019s founding principle of addressing quality-related issues in life science facilities, the site provides practical, expert-led information for life science manufacturing professionals. With more than 26,000 registered users, GMP Platform introduces the latest GMP-related regulations and trends in Japan, the United States, Europe, and other regions, along with translated and explanatory articles on guidelines, technical articles, seminars, e-learning programs, and books. It is widely used by professionals involved in GMP compliance, quality assurance, and the development of effective quality systems.Please use Google Translate or similar translation tools to read more articles originally published in Japanese.
\n*If you are using Google Chrome, right-click and select “Google Translate” on the article.<\/div>\n<\/div>\n","protected":false},"featured_media":6290,"template":"","columncat":[61],"columntag":[],"keywords":[11,14],"acf":[],"yoast_head":"\nFundamentals of Microbiology [Part 7]\uff5cCM Plus<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/cm-plus.co.jp\/en\/column\/gmp\/2026_1102\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Fundamentals of Microbiology [Part 7]\uff5cCM Plus\" \/>\n<meta property=\"og:description\" content=\"What Are Bacteria 2-2 Bacteria proliferate by division when the surrounding environment such as temperature, nutrients, oxygen, or osmotic pressure is suitable for the bacteria. 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