an overview of microbial life chapter 2. 3 domains: archae, eubacteria, eukaryota two structural...

An Overview of Microbial Life

Chapter 2

3 Domains: Archae, Eubacteria, Eukaryota Two structural types of cells are recognized:

the prokaryote and the eukaryote. Prokaryotic cells have a simpler internal

structure than eukaryotic cells, lacking membrane-enclosed organelles.

Viruses:– Viruses are not cells but depend on cells for their

replication.

Elements of Cell and Viral Structures:

Cells from each domain

BacteriaArchae

Eukarya

The basic components.. All microbial cells share

certain basic structures in common, such as cytoplasm, a cytoplasmic membrane, ribosomes, and (usually) a cell wall. – Note: Animal cells typically

do not have a cell wall The major components

dissolved in the cytoplasm include– Macromolecules– Inorganic ions

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Eukaryotic Cells

Larger and structurally more complex

Euk. microorganisms include algae, fungi and protozoa

Membrane enclosed organelles– Nucleus– Mitochondria– Chloroplasts

(photosynthetic cells only)

Prokaryotic Cells

Lack membrane enclosed organelles Include Bacteria and Archae Smaller than eukaryotic cells (Typically ~1-5

um long and ~1um in width) However, can vary greatly in size

Viruses

Not cells Static structures which

rely on cells for replication and biosynthetic machinery

Many cause disease and can have profound effects on the cells they infect– Cancer, HIV

However, can alter genetic material and improve the cell

Arrangement of DNA in Microbial Cells Genes govern the properties of cells, and a

cell's complement of genes is called its genome.

DNA is arranged in cells to form chromosomes.

In prokaryotes, there is usually a single circular chromosome; whereas in eukaryotes, several linear chromosomes exist.

Nucleus vs. Nucleoid

Nucleus: a membrane-enclosed structure that contains the chromosomes in eukaryotic cells.

Nucleoid: aggregated mass of DNA that constitutes the chromosome of cells of Bacteria and Archaea



Prokaryotic DNA

Most DNA is circular Most have only a single chromosome Single copy of genes

– Haploid Many also contain plasmids

Plasmids

Plasmids are circular extrachromosomal genetic elements (DNA), nonessential for growth, found in prokaryotes.

Typically contain genes that confer special properties (ie unique metabolic properties)

Useful in biotechnology



Eukaryotic DNA

Organized into linear molecules Packaged into chromosomes

– Number varies Typically contain two copies of each

gene– Diploid

Genes, genomes, and proteins

E.coli genome= a single circular chromosome of 4.68 million base pairs

# of genes: 4,300 A single cell contains:

– 1,900 different proteins– 2.4 million protein molecules– Abundance of proteins varies

Genome size, complexity, and the C-value paradox

Genome size does not necessarily correlate with organismal complexity



In actuality….



Evolution: change in allelic frequencies over generations

The evolutionary relationships between life forms are the subject of the science of phylogeny.

Phylogenetic relationships are deduced by comparing ribosomal sequences

The Tree of Life

The three domains of life

Comparative ribosomal RNA sequencing has defined the three domains of life: Bacteria, Archaea, and Eukarya.

What has this sequencing revealed?? Molecular sequencing has shown that the

major organelles of Eukarya have evolutionary roots in the Bacteria

Mitochondria and chloroplasts were once free-living cells that established stable residency in cells of Eukarya eons ago. – The process by which this stable arrangement

developed is known as endosymbiosis.

What has this sequencing revealed?? Cont. Although species of Bacteria and

Archaea share a prokaryotic cell structure, they differ dramatically in their evolutionary history.

Archae are more closely related to eukaryotes than are species of bacteria

Molecular sequencing and microbiology Overall rRNA sequencing technology has

helped reveal the overall evolutionary connections between all cells– In particular prokaryotes

Impacted subdispiciplines– Microbial classification and ecology– Clinical diagnostics

Can identify organisms without having to culture them

Microbial Diversity

Cell size and morphology Metabolic strategies (physiology) Motility Mechanisms of cell division Pathogenesis Developmental biology Adaptation to environmental extremes And many more

Physiological Diversity of Microorganisms

All cells need carbon and energy sources

Energy can be obtained in 3 ways:– Organic chemicals– Inorganic chemicals– Light

Types of physiological diversity:– Chemoorganotrophs– Chemolithotrophs– Phototrophs– Heterotrophs and Autotrophs– Habitats and Extreme environments



Chemoorganotrophs

Chemoorganotrophs obtain their energy from the oxidation of organic compounds. – Energy conserved as ATP

All natural and even synthetic organic compounds can be used as an energy source

Aerobes Anaerobes Most microorganisms that have been cultured

are chemoorganotrophs

Chemolithotrophs

Chemolithotrophs obtain their energy from the oxidation of inorganic compounds.

Found only in prokaryotes Can use a broad spectrum of inorganic

compounds Advantageous because can utilize

waste products of chemoorganotrophs

Phototrophs

Phototrophs contain pigments that allow them to use light as an energy source. – ATP generated from light energy– Cells are colored

Oxygenic photosynthesis: – O2 involved– Cyanobacteria and relatives

Anoxygenic photosynthesis:– No O2

– Purple and green bacteria

Autotrophs and Heterotrophs

All cells require carbon as a major nutrient Microbial cells are either:

– Autotrophs use carbon dioxide as their carbon source, whereas heterotrophs use organic carbon from one or more organic compounds.

– Autotrophs considered primary producers• Synthesize organic matter from CO2 for themselves and

that of chemoorganotrophs• All organic matter on earth has been synthesized from

primary producers

Habitats and Extreme Environments Microorganisms are everywhere on Earth

that can support life Extremophiles: organisms inhabiting

extreme environments – Boiling hot springs,– Within ice, extreme pH, salinity, pressure



Examples of Extremophiles:

Prokaryotic Diversity

Several lineages are present in the domains Bacteria and Archaea

An enormous diversity of cell morphologies and physiologies are represented

rRNA analysis has shown dramatic differences in phenotypic characteristics within a given phylogenetic group

Bacteria

Proteobacteria The Proteobacteria is the largest division (called a

phylum) of Bacteria A major lineage of bacteria that contains a large

number of gram(-) rods and cocci Represent majority of known gram(-) medical,

industrial, and agricultural bacteria of significance Extreme metabolic diversity:

– Chemorganotrophs: E.coli– Photoautotrophs: Purple sulfur bacterium– Chemolithotrophs: Pseudomonas, Aztobacter– Pathogens: Salmonella, Rickettsia, Neisseria

Proteobacteria examples



Chemolithotrophic sulfur-oxidizing bacteria Achromatium

Neisseria gonorrhoeae

Gram-positive bacteria

United by a common cell wall structure Examples: Spore forming:

– Clostridium, Bacillus Antibiotic producing:

– Streptomyces Lactic acid bacteria:

– Streptococcus– Lactobacillus

Mycoplasmas:– Lack cell wall– Small genomes – Often pathogenic

Cyanobacteria

The Cyanobacteria are phylogenetic relatives of gram-positive bacteria and are oxygenic phototrophs.

First oxygenic phototrophs to have evolved on Earth

Planctomyces

Characterized by distinct cells with stalks that allow for attachment to solid surfaces

Aquatic

Spirochetes

Helical shaped Morphologically and

phylogenetically distinct

Widespread in nature and some cause disease– Most notable sp

cause Syphilis and Lyme Disease

Spirochaeta zuelzerae

Green sulfur and non-sulfur bacteria Contain similar

photosynthetic pigments

Can grow as autotrophs Chloroflexus

– Inhabits hot springs and shallow marine bays

– Dominant organism in stratified microbial mats

– Important link in the evolution of photosynthesis

Chlamydia

Most species are pathogens

Obligate intracellular parasites

How would this affect an immune response?



Deinococcus

Contain sp with unusual cell walls and high level of resistance to radiation

Cells usually exist in pairs or tetrads

Can reassemble its chromosome after high radiation



Aquifex, Thermotoga, Env-OP2

Sp that branch early on the tree

Unified in that they grow at very high temps: hyperthermophily

Inhabitats of hot springs

Archaea

There are two lineages of Archaea: the Euryarchaeota and the Crenarchaeota

Many are extremophiles All are chemotrophic

– Many using organic carbon

– While others are chemolithotrophs

Euryarchaeota & Crenarchaeota

Physiologically diverse groups

Many inhabit extreme environments– From extreme pH,

temperature, salinity

Limitations of Phylogenetic analyses Not all Archaea are extremophiles Difficult to culture Based on molecular microbial ecology,

the extent of diversity is much greater than once thought

Eukaryotic Microorganisms

Collectively, microbial eukaryotes are known as the Protista.

Microbial eukaryotes are a diverse group that includes algae, protozoa, fungi, and slime molds

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

The “early-branching” Eukarya are structurally simple eukaryotes lacking mitochondria and other organelles– Ex Giardia

Eukaryotic microbial diversity

Eukaryotic microbial diversity Diplomonads: flagellates, many are parasitic

– Ex: Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite flagellated protozoan parasite

Trichomonads: anaerobic protist, many are pathogenic– Ex. Trichomonas vaginalis

Flagellates: all protozoa in this group utilize flagella for motility, free-living, and pathogenic– Ex. Trypanosomes

Slime molds: resemble fungi and protozoa– Ex. Dictyostelium discoideum

Algae

Fungi

Protozoa

Lichens

Some algae and fungi have developed mutualistic associations called lichens.



an overview of microbial life chapter 2. 3 domains: archae, eubacteria, eukaryota two structural...

Documents

chromosome of cells

properties of cells

animal cells

single cell

cell arrangement of

elements of cell

membraneenclosed structure

single circular chromosome