首页 | 家园 | 百科 | 下载 | 书库 | 仪器 | 展会 |人才 | 公司 | 网址 | 问答 | 论坛 | 注册 | 通行证登录 | English

生物行

生物行   进展 | 摘要 | 人物 | 医药 | 疾病 | 技术 | 健康 | 能源   生物航   供应 | 求购 | 公司 | 展会 | 要发布
论坛   神经科学 | 神经系统疾病 | 实验技术 | 求职招聘 | 器材试剂 | 文献检索 | 读书笔记 | 考试招生 | 软件使用
当前位置: 主页 > 生物技术 > 基本实验 >

A good introduction to Microbiology

时间:2006-01-12 09:04来源:Internet 作者:bioguider 阅读:

Introduction

An initial aim of all microbiologists is the reproducible growth of their microbial cultures, no matter whether the microorganisms are of natural origin or have been genetically engineered by man. Reproducible growth requires defined environmental conditions with respect to energy source, temperature, pH and nutrients (see chapter Microbial Growth Requirements). With this in mind Fluka supplies a range of products and services (see list of culture collections, comparison of media etc.) designed to meet the needs of general microbiologists and specialists alike.

Microorganisms

In the group of organisms classified as microorganisms, there are simple unicellular forms (cocci, bacilli, virio and spirillae) as well as multicellular forms (filaments and sheaths). The group includes the blue green algae (cyanobacteria), fungi, protozoans and bacteria.

In order to survive and grow, microorganisms require a source of energy and nourishment. Bacteria are the most primitive forms of microorganisms but are composed of a great variety of simple and complex molecules and are able to carry out a wide range of chemical transformations. Depending on their requirements and the source of energy used they are classified into different nutritional groups.

The size of microorganisms varies from a fraction of a μm for viruses, which can only be seen in the electron microscope, to several cm for filamentous algae or fungi, for example:

Organisms Size range (μm) Example (size in μm)

Prokaryotes
Bacterium: typical rod 1.0-0.5 x 1.0-10 Pseudomonas aeruginosa (1.5 x 0.5)
Bacillus megaterium (7.6 x 2.4)
Bacterium: typical sphere 1.0 diam
Eukaryotes
Fungi: filamentous 8-15 x 4-8 Mucor hiemalis (8 diam)
Fungi: yeast cell Saccharomyces cerevisiae (29-49.1 μm3)
Alga 28-32 x 8-12 Chlamydomonas
Viruses
Virus 0.015 x 0.3 Poliovirus (0.03 x 0.03)
Tobacco mosaic (0.02 x 0.3)


Microbial Growth Requirements

Microbial growth requires suitable environmental conditions, a source of energy, and nourishment. These requirements can be divided into two categories, physical and chemical.

Chemical Factors

Table of the elements required for microbial growth as found in nature compared to the chemical forms supplied to microbiological media.

(责任编辑:泉水)
Requirements for Growth Form usually found in
Nature
Chemical Form commonly
added to Microbiological Media

Carbon Carbon dioxide (CO2), HCO3-
organic compounds
Organic; simple sugars e.g.
glucose, acetate or pyruvate; extracts such as peptone,
tryptone, yeast extract etc.
Inorganic; carbon dioxide (CO2)
or hydrogen carbonate salts (HCO3-)*
Hydrogen Water (H2O)
organic compounds
Oxygen Water (H2O), oxygen gas (O2),
organic compounds
Nitrogen Ammonia (NH3), nitrate (NO3-)
organic compounds
e.g. amino acids
nitrogen gas (N2)
Organic; amino acids,
nitrogenous bases
Inorganic; NH4CI, (NH4)2S04, KNO3, and for dinitrogen fixers N2
Phosphorus Phosphate (PO43-) KH2PO4, Na2HPO4*
Sulphur Hydrogen sulphide(H2S),
sulphate (SO42-),
organic compounds
e.g cysteine
Na2SO4, H2S
Potassium K+ KCI, K2HPO4*
Magnesium Mg2+ MgCI2, MgSO4
Calcium Ca2+ CaCI2, Ca(HC03)2*
Sodium
------分隔线----------------------------
发表评论
请自觉遵守互联网相关的政策法规,严禁发布色情、暴力、反动的言论。
评价:
表情:
用户名: 验证码:点击我更换图片