In natural environment, microbial cells will almost always be in mixed cultured. They have to interact each other, but these interaction are limited by the potential of each cell.
Each species of the environmental microbe has specific potential and some of them are potential to produce useful industrial products.

The microorganisms encompass the three groups:
Viruses, Prokaryotes, and Eukaryotes
Other microbiologists claim three Kingdoms of five Kingdoms of cellular life are microorganisms, namely:
Monera : bacteria (procaryotae) and blue green algae
Protista : protozoa, eukaryotic algae, slime
Fungi moulds and flagellated fungi
: non-flagellated fungi

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It is not having a cell structure
It is dependent on its host’s metabolic machinery
Its structure of nucleic acid, DNA or RNA, is surrounded by protein and sometimes an outer lipid-rich envelope

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Purple bacteria and the green bacteria
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Gliding bacteria
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Sheathed bacteria
Spirochaetes
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Spiral and curve bacteria
Gram-negative aerobic rods and cocci
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Gram-negative facultative anaerobic rods
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Gram-negative anaerobic bacteria
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Methane producing bacteria
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Gram-positive cocci
Gram-positive endospore-forming rods and cocci
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Group of Lactobacillaceae
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Actinomycetes
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Rickettsias
Mycoplasmas
Cyanophyceae or Cyanobacteria

The students are divided into several groups and each group…

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Bacteria are unicellular, most ca. 0.5-1.0 x 2.0-10 µm in size.
They can be motile or non-motile
Cytoplasmic materials are enclosed in a rigid wall on they are immobile.
The membrane contains energy generating components.
The genetic materials (structural and plasmid DNA) are circular, not enclosed in nuclear membrane, and do not contain basic protein such as histones.
Cell division is by binary fission.
Can also have flagella, capsules, surface layer protein, and pili for specific function.
Some also form endospores (one per cell)
Gram-positive cells or Gram-negative cells

If we look at the shape and size, called
for grouping the bacteria. The most common shapes are rod-like, bacillus
(plural: bacilli), and sperichal, coccus
(plural: cocci)
look like cocci) to very long filaments. Also form spiral and corkscrew, oval (coccoid), comma, and branch structure.

Eukaryotic cells:
 are generally much larger than prokaryotic cells
 have rigid cell walls and thin plasma membranes
(contain sterol)
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 the cell wall does not have mucopeptide and is composed of carbohydrates the cytoplasm is mobile (streaming) and contain organelles
 the DNA is linear (chromosomes), contains histones, and is enclosed in a nuclear membrane.
The eukaryotic microorganisms are:
Fungi
Algae
Protozoa

Yeasts – unicellular
Molds – multicellular
Molds
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 are non-motile, filamentous and branches the cell wall is composed of cellulose, chitin, or both are composed of hyphae (large number of
 mycellium.
a hyphae can be vegetative or reproductive,
(sporangium). Shape, size and color of spores are used for taxonomic classification.

Yeast
 the cells are oval, spherical, or elongated (5-
30 x 2-10 µm), non-motile.
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 the cell wall contains polysaccharides
(glycans), protein and lipids.
the cytoplasm has a finely granular appearance for ribosomes and organelles.
the nucleus is well defined with nuclear membrane

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The algae are photosynthetic eukaryotic microorganisms.
The major primary producers in the sea and in lakes, but are also found in the surface layer of soil.
Many can live heterotrophically.

The algae have been classified traditionally by pigmentation and life cycle:
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Rhodophyceae, the red algae: marrine, multicellular, immotile, some unicellular
Chlorophyceae: many planktonic species, freshwater and marine, motil by flagella,multicellular.
Prasinophyceae: unicellular planctonic flagellated organisms, marine.
Euglenophyceae: unicells, motile by single flagellum, common in nutrition rich freshwater pools, also found in the sea and in the soil.
Bacillarophyceae, diatoms: in mcroplankton of sea and lakes, motile.
Dinophyceae, dinoflagellates: in microplankton of seas and lake s, motile, some are non photosynthetic.
Crysophyceae: found in freshwater, also the marine silicoflagellates, biflagellate cells.
Haptophyceae: biflagellate planktonic algae, in marine, blooms of this species can give the sea a milky appearance.
Cryptophyceae: unicellular flagellates found as minor components of plankton.

algae… classified traditionally…:
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Xanthophyceae: multicellular, but few unicellular in plankton and soil.
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Eustigmatophyceae: unicellular, in freshwater, sometime found in soil.
Among aquatic microorganisms microalgae are a very interesting source of a wide range of compounds. They do not only have the capacity to produce high-value compounds, but also the ability to do it using only sunlight, carbon dioxide and sea water.

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Peptides and protein: lectins (glycoprotein) have proved to be useful for clinical diagnosis and other health application. Red algae (Bryothamnion triquetrum, Solieria
robusta, Ceratodiction spongiosum)
 -carotene/canthaxanthin and astaxanthin: green-algae, Haematococcus pluvialis.
Seaweed polysaccharides
Lipid – polyunsaturated fatty acid

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Exhibit a very wide range of form and way of life.
Many are predators on bacteria, fungi, algae, yeast, or other protozoa, while some others are parasitic in animals.
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Sarcomastigophora: the flagellated cells and amoeboid protozoa, some are human pathogens such as Trypanosoma brucei in the bloodstream, and
Entamoeba histolytica in the gut. Some flagellates are symbionts in termite guts.
Ciliphora: includes the familiar ciliates, Tetrahymena and Paramecium. Vorticella species are very important in sewage treatment processes.
Sporozoa: totally endoparasitic in animals or man,
Plasmodium cause malaria.

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› pH (acidity)
› Water Activity (moisture)
› Oxidation-reduction potential (oxygen or ionic)
› Nutrition (food)

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Environment factors that influence microbial growth are considered extrinsic factors, such as:
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Temperature
 Each species of microbe has an optimal temperature of growth
 Temperature regulate the expression of gene
 The growth temperature can also influence a cell’s thermal sensitivity.
Gas composition
 It relates to the oxygen concentration. Many microbes are inhibited in low concentration or without of oxygen, but some may grow even though in the absent of oxygen.
 It is applied in food preservation using controlled or modified atmosphere storage.

Four phase of microbial growth:
Log
Total mikroba
Fase lag Fase logaritmik
Fase stasioner Fase kematian
Waktu

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During the log, or exponential, growth phase microbes (bacteria) reproduce by binary fision. Thus, during this phase, firstorder reaction can be used to describe the change in cell number
The number of microbes (N) at any time is directly proportional to the initial number of microbes (N o
)
The microbiologists frequently use td to describe growth rates of microbes and µ to describe specific growth rates

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The killing of microbes by energy input, acid, bacteriocin, and other lethal agents is also governed by first-order kinetics
By this kinetic reaction, it can be predicted the number of microbes (viable cells) remaining after treatment, such as in sterilization process.
In microbiology, D value (amount of time required to reduce N o by 90%) is the most frequently used as kinetic constant. D values are inversely proportional to the rate constant, k, for a given temperature.

Growth a Thermal inactivation b Iradiation c
N = N o e
µt
2.3log(N/N o
) = µ∆t
N = N o e -kt
2.3log(N/N o
) = -(k ∆t)
N = N o e -D/Do
∆t = [2.3 log(N/N o
)]/ µ ∆t = -[2.3 log(N/N o
)]/k t d
= 0.693/ µ D = 2.3/k a N, cell number (cfu/g); No, initial cell number (cfu/g); t, time (h); µ, specific growth rate (h -1 ); t d, doubling time (h); b k, rate constant (h -1 ); D, decimal reduction time (h); c Do, rate constant (h -1 );
D, dose (Gy)
µ (h -1 ) t d
(h) Organism
Bacteria
Optimal conditions
Limited nutrients
Psychotroph, 5 o C
Molds, optimal
2.3
0.20
0.023
0.1 – 0.3
0.3
3.46
30
6.9 – 20

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The availability of suitable nutrients is clearly a major factor determining whether the microbes will grow or not in a particular environment.
There are four useful ways to classify potential nutrient mlocules:
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As esential, or useful but dispensable
Used as building blocks for macromolecules, or as energy sources, or as both
As macronutrient required in large quantities, or as micronutrients
As macromolecules requiring breakdown before entry to the cell, or small molecules readily entering as soluble nutrients.
The major elements of the cell are carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorous.

 utilized as sources of carbon. Organic acids are readily used directly as sources of carbon by most
 microbes.
Nitrogen is abundant as gaseous dinitrogen, but
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 nucleotides, uric acid and urea, can also provide cells’ requirements for nitrogen.
Some organisms can utilize hydrogen sulphide as source of sulphur. Organic sulphur as amino acids cysteine and methionine can also be used.
phosphate.