1896 1920 1987 2006

Lecture 2

An Overview of Microbial

Life

Zhao Liping, Chen Feng

School of Life Science and Technology

Shanghai Jiao Tong University

http://micro.sjtu.edu.cn

Chapter 2 inBROCK BIOLOGY OF MICROORGANISMS

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I. Cell Structure and Evolutionary

History

Most of the microbial cells are prokaryotic cells原核

细胞

Some microorganisms have eukaryotic cell structure

真核细胞

Some microorganisms are non-cellular life forms非细

胞生物

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2.1 Elements of Cell and Viral Structures

Internal structure of microbial cells. Prokaryote cells lack a true

nucleus and organelles原核细胞无真正的细胞核及细胞器

Eukaryote cell possesses a true nucleus and organelles

真核生物具有细胞核及细胞器

Eukaryotic cells真核

Algae藻类

Fungi真菌

Molds丝状真菌

Yeasts

Protozoa原生生物

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Non-cellular life forms: virus 病毒

A single virus particle is about 65nm in diameter.

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Nucleoid : aggregated DNA /bacterial chromosome

in the prokaryotic cell 类核：用于描述原核细胞中

聚集在一起的DNA

2.2 Arrangement of DNA in Microbial

Cells: Bacterial Nucleoid

By gently lysing the cells, the highly compacted

nucleoid will emerge intact. 采用极轻微小心的细胞

裂解方法，就可以得到一团完整展开的类核DNA。

(Arrows

point to edge

of strands).

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Bacteria contain one long circular DNA-

chromosome. 细菌的类核包含一条环状的DNA

(染色体)

The DNA can be 1mm long

The cell is usually 2-3m long

The DNA in both the open circle and supercoiled chromosome is

present in a covalently closed form. 超螺旋

The double-stranded DNA in E. coli chromosome contains over

50 supercoiled domains.超螺旋域

Genome sizes vary greatly ranging from viruses with the

smallest to algae and vertebrates possessing the

greatest amount.病毒基因组最小,藻类、脊椎动物最大

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2.3 Tree of Life

Evolution is the change in a line of descent over

time leading to new species or varieties.演化/进化

Evolutionary relationships between life forms are

the subject of phylogeny.系统发生学

Phylogenetic relationships can be deduced by

comparing sequences of certain macromolecules

(ribosomal RNAs).

Ribosomal RNA gene sequencing and phylogeny.

(a) Cells, either from a pure culture or from an environmental sample, are broken open;(b) the gene-encoding ribosomal RNA is isolated, and many identical copies

made by polymerase chain reaction (PCR)(c) The gene is sequenced(d) the sequences obtained are aligned in a computer.

（e) An algorithm makes a tree that shows the differences in rRNA sequence

between the organisms analyzed. 对比不同生物之间rRNA的差异,可得到描述其两两差异的树状结构.

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Phylogenetic tree of life as defined by comparative ribosomal

RNA sequencing. three domains of organisms: the bacteria and the

Archaea, cells of which are prokaryotic, and the Eukarya (eukaryotes).三域:

细菌, 古生菌与真核生物.

1896 1920 1987 2006

PART II Microbial Diversity

2.4 Physiological Diversity of Microorganisms

微生物的生理多样性

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All cells need carbon and

energy sources.

Chemoorganotrophs obtain

their energy from the

oxidation of organic

compounds.化能有机营养型.

Chemolithotrophs obtain

their energy from the

oxidation of inorganic

compounds.化能无机营养型

Phototrophs contain

pigments that allow them to

use light as an energy source.

光能营养型

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Autotrophs and heterotrophs

Autotrophs use CO2 as their carbon source, whereas

heterotrophs use organic carbon. 自养型生物以CO2

为碳源, 异养型生物以有机碳为碳源.

Depend on the carbon source.

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2.5 Prokaryotic Diversity

Several lineages are present in the domains

Bacteria and Archaea, and an enormous diversity of

cell morphologies and physiologies are represented

there. 细胞形态及生理的多样性

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Microbial cells: Bacteria

Pathogens

Soils, water, animal intestine, etc

Different energy sources, carbon sources, oxygen

demands

Detailed phylogenetics tree of Bacteria

产液菌属

栖热袍菌属

无硫绿细菌

异常球菌

螺旋体绿硫细菌

浮霉状菌属

蓝细菌

变形杆菌

革兰氏阳性细菌

Proteobacteria: the largest

division (called a phylum门) of

Bacteria.变形杆菌

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Cyanobacteria蓝细菌

The Cyanobacteria are phylogenetic relatives

of gram-positive bacteria and are oxygenic

phototrophs.

Filamentous cyanobacteria 丝状蓝细菌

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Microbial cells: Archaea

Many are extremephiles, anerobic

• Boiling-hot spring

• Freezing-Antarctic ocean

• Radioactive wastes

• Salty, acidic, alkaline soils or water

They can be found almost anywhere on earth

There are two lineages of Archaea, the Euryarchaeota and the

Crenarchaeota. 古生菌有广古生菌界与泉古生菌界.

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Molds

Mushrooms Fungi

Yeasts

Slime molds

Algae

Protozoa

2.6 Eukaryotic Microorganisms

Cells of algae and fungi have cell walls, whereas the protozoa do not.

Fungi are heterotrophic eukaryotic microorganisms.

They are nonphotosynthetic and typically form

reproductive spores.真菌为异养真核生物,非光合,一般可形成繁殖的孢子.

Algae are phototrophic eukaryotes that contain

photosynthetic pigments within chloroplast藻类是光合真核生物,在其叶绿体中有光合色素.

Protozoa are animallike protists exhibiting

heterotrophic nutrition and they can be defined as

usually motile eukaryotic unicellular microorganisms.

原生生物是类似动物的低等异养真核生物, 常定义为可运动的单细胞真核微生物.

Detailed phylogenetic tree of Eukarya

双滴虫 微孢子虫

鞭毛虫

粘质霉菌

硅藻

褐藻

纤毛虫

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Algae 藻类 Fungi 真菌

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Protozoa 原生生物

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a)Amoeba变形虫

b)A typical ciliate典型的纤毛虫

c) A flagellate鞭毛虫

Some algae and fungi have developed mutualistic associations

called lichens. 一些藻类与真菌共生而形成地衣

Some algae and fungi have developed mutualistic associations

called lichens. 一些藻类与真菌共生而形成地衣

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Discussion

What kinds of organisms belong to the

Microorganisms?

Different between mould, cyanobacteria and

algae?

Different between yeast, mould and mushroom?

Different between protozoa, yeast and animal?

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