• Tidak ada hasil yang ditemukan

Toxic Forms of Oxygen

N/A
N/A
Protected

Academic year: 2019

Membagikan "Toxic Forms of Oxygen"

Copied!
10
0
0

Teks penuh

(1)

M I C R O B I O L O G Y

a n i n t r o d u c t i o n

ninth edition TORTORA⏐FUNKE⏐CASE

6

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint®Lecture Slide Presentation prepared by Christine L. Case

6

Microbial

Growth

ƒ Microbial growth is the increase in number of cells, not cell size

Microbial Growth

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

The Requirements for Growth:

Physical Requirements

ƒ Temperature

ƒMinimum growth temperature

ƒOptimum growth temperature

ƒMaximum growth temperature

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

g p

Temperature

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.1

Psychrotrophs

ƒ Grow between 0°C and 20-30°C

ƒ Cause food spoilage

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Psychrotrophs

(2)

The Requirements for Growth:

Physical Requirements

ƒ pH

ƒMost bacteria grow between pH 6.5 and 7.5

ƒMolds and yeasts grow between pH 5 and 6

ƒAcidophiles grow in acidic environments

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

p g

The Requirements for Growth:

Physical Requirements

ƒ Osmotic pressure

ƒHypertonic environments, increase salt or sugar, cause plasmolysis

ƒExtreme or obligate halophiles require high osmotic

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

g p q g

pressure

ƒFacultative halophiles tolerate high osmotic pressure

The Requirements for Growth:

Physical Requirements

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.4

The Requirements for Growth:

Chemical Requirements

ƒ Carbon

ƒStructural organic molecules, energy source

ƒChemoheterotrophs use organic carbon sources

ƒAutotrophs use CO2

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

p 2

The Requirements for Growth:

Chemical Requirements

ƒ Nitrogen

ƒIn amino acids and proteins

ƒMost bacteria decompose proteins

ƒSome bacteria use NH4+or NO3–

ƒA few bacteria use N2in nitrogen fixation

S lf

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings ƒ Sulfur

ƒIn amino acids, thiamine and biotin

ƒMost bacteria decompose proteins

ƒSome bacteria use SO42–or H2S

ƒ Phosphorus

ƒIn DNA, RNA, ATP, and membranes

ƒPO43–is a source of phosphorus

The Requirements for Growth:

Chemical Requirements

ƒ Trace elements

ƒInorganic elements required in small amounts

ƒUsually as enzyme cofactors

(3)

The Requirements for Growth:

Chemical Requirements

ƒ Oxygen (O2)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 6.1

Toxic Forms of Oxygen

ƒ Singlet oxygen: O2boosted to a higher-energy state

ƒ Superoxide free radicals: O2–

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒ Peroxide anion: O22–

ƒ Hydroxyl radical (OH•)

The Requirements for Growth:

Chemical Requirements

ƒ Organic growth factors

ƒOrganic compounds obtained from the environment

ƒVitamins, amino acids, purines, and pyrimidines

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Culture Media

ƒ Culture medium: Nutrients prepared for microbial growth

ƒ Sterile: No living microbes

ƒ Inoculum: Introduction of microbes into medium

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒ Culture: Microbes growing in/on culture medium

Agar

ƒ Complex polysaccharide

ƒ Used as solidifying agent for culture media in Petri plates, slants, and deeps

ƒ Generally not metabolized by microbes

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

y y

ƒ Liquefies at 100°C

ƒ Solidifies ~40°C

Culture Media

ƒ Chemically defined media: Exact chemical composition is known

ƒ Complex media: Extracts and digests of yeasts, meat, or plants

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

p

ƒNutrient broth

(4)

Culture Media

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Tables 6.2, 6.4

Growth in Continuous Culture

ƒ A “continuous culture” is an open system in which

fresh media is continuously added to the culture at

a constant rate, and old broth is removed at the

same rate.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒ This method is accomplished in a device called a

chemostat.

ƒ Typically, the concentration of cells will reach an

equilibrium level that remains constant as long as

the nutrient feed is maintained.

Basic Chem ost at Syst em

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Our Ch em ost at Syst em

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Anaerobic Culture Methods

ƒ Reducing media

ƒContain chemicals (thioglycollate or oxyrase) that combine O2

ƒHeated to drive off O2

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 2

Anaerobic Culture Methods

ƒ Anaerobic jar

(5)

Anaerobic Culture Methods

ƒ Anaerobic chamber

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.6

Capnophiles Require High CO

2

ƒ Candle jar

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒ CO2-packet

Figure 6.7

Selective Media

ƒ Suppress unwanted microbes and

encourage desired

microbes.

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.9b–c

Selective Media

ƒ Inhibits the growth of some bacteria while selecting for the growth of others

ƒ Example:

ƒBrilliant Green Agar

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

g

ƒdyes inhibit the growth of Gram (+) bacteria

ƒselects for Gram (-) bacteria

ƒMost G.I. Tract infections are caused by Gram (-) bacteria

Selective Media

ƒ EMB (Eosin Methylene Blue)

ƒdyes inhibit Gram (+) bacteria

ƒselects for Gram (-) bacteria

ƒG.I. Tract infections caused by Gram (-)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

y ( )

bacteria

Differential Media

ƒ Make it easy to distinguish colonies of different microbes.

(6)

Some media are both selective and

differential

ƒMannitol salt agaris both selective and differential

ƒSelective:

ƒStaphylococcus aereuscan grow on mannitol salt agar that has a high concentration of salt; the growth of other organisms will be inhibited

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings inhibited

ƒDifferential:

ƒStaphylococcus aureusferments mannitol and the medium will change color

ƒOther organisms that grow on high salt will grow on mannitol salt agar but may not ferment mannitol; the media will not change colors

Selective and Differential Media

ƒ Mannitol Salt Agar

ƒused to identify Staphylococcus aureus

M i l S l A

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒ Mannitol Salt Agar

ƒHigh salt conc. (7.5%) inhibits most bacteria

ƒsugar Mannitol

ƒpH Indicator (Turns Yellow when acid)

Selective and Differential Media

ƒ MacConkey’s Agar

ƒused to identify Salmonella

ƒ MacConkey’s Agar

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒBile salts and crystal violet (inhibits Gram (+) bacteria)

ƒlactose

ƒpH Indicator

Many Gram (-) enteric non-pathogenic bacteria can ferment lactose, Salmonella can not

Enrichment Media

ƒ Encourages growth of desired microbe

ƒ Assume a soil sample contains a few phenol-degrading bacteria and thousands of other bacteria

ƒInoculate phenol-containing culture medium with the soil and incubate

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

soil and incubate

ƒTransfer 1 ml to another flask of the phenol medium and incubate

ƒTransfer 1 ml to another flask of the phenol medium and incubate

ƒOnly phenol-metabolizing bacteria will be growing

ƒ A pure culture contains only one species or strain.

ƒ A colony is a population of cells arising from a single cell or spore or from a group of attached cells.

ƒ A colony is often called a colony-forming unit (CFU).

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

y y g ( )

Streak Plate

(7)

Preserving Bacteria Cultures

ƒ Deep-freezing: –50°to –95°C

ƒ Lyophilization (freeze-drying): Frozen (–54° to –72°C) and dehydrated in a vacuum

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Reproduction in Prokaryotes

ƒ Binary fission

ƒ Budding

ƒ Conidiospores (actinomycetes)

ƒ Fragmentation of filaments

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

g

Binary Fission

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.11 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.12b

ƒ If 100 cells growing for 5 hours produced 1,720,320 cells:

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

PLAY Animation: Bacterial Growth

(8)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.14

1. Lag Phase

ƒ Bacteria are first introduced into an environment or media

ƒ Bacteria are “checking out” their surroundings

ƒ cells are very active metabolically

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

y y

ƒ # of cells changes very little

ƒ 1 hour to several days

2. Log Phase

ƒ Rapid cell growth (exponential growth)

ƒ population doublesevery generation

ƒ microbes are sensitive to adverse conditions

ƒantibiotics

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒanti-microbial agents

3. Stationary Phase

ƒ Death rate = rate of reproduction

ƒ cells begin to encounter environmental stress

ƒlack of nutrients

ƒlack of water

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒnot enough space

ƒmetabolic wastes

ƒoxygen

ƒpH

Endospores would form now

4. Death Phase

ƒ Death rate > rate of reproduction

ƒ Due to limiting factors in the environment

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Measuring Microbial Growth

Direct methods

ƒ Plate counts

ƒ Filtration

ƒ MPN

Indirect methods

ƒ Turbidity

ƒ Metabolic activity

ƒ Dry weight

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

ƒ Direct microscopic count

ƒ Dry weight

(9)

Direct Measurements of Microbial Growth

ƒ Plate counts: Perform serial dilutions of a sample

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.15, step 1

Plate Count

ƒ Inoculate Petri plates from serial

dilutions

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.16

Plate Count

ƒ After incubation, count colonies on plates that have 25-250 colonies (CFUs)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.15

Direct Measurements of Microbial Growth

ƒ Filtration

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.17

Direct Measurements of Microbial Growth

ƒ Multiple tube MPN test.

ƒ Count positive tubes and

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

compare to

statistical

MPN table.

Figure 6.18b

Direct Measurements of Microbial Growth

ƒ Direct microscopic count

(10)

Direct Measurements of Microbial Growth

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.19, steps 1, 3

Estimating Bacterial Numbers

by Indirect Methods

ƒ Turbidity

Gambar

Figure 6.6Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 6.7
Figure 6.10a–b
Figure 6.11Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 6.12b
Figure 6.15, step 1
+2

Referensi

Dokumen terkait

CHOERI Fiqih MI Roudlotut Tholibin Ash Shodiqin Maibit Rengel Tuban 24 25 13050623720009 ISBAH Fiqih MTs Muhammadiyah 1 Karangagung Palang Tuban 25. LPTK IAIN SUNAN

Saat diskusi memang karekter anak berbeda-beda, ada yang aktif ada juga yang pasif, untuk mengatasi anak yang pasif biasanya saya menunjuk anak tersebut dan

Tempat : Kantor Bagian Ekonomi dan Pembangunan Sekretariat Daerah Kabupaten Bone Bolango d/a Desa Ulanda Kecamatan Suwawa Kabupaten Bone Bolango. Diharapkan

Ditinjau dari karakteristik padatan yang mengandung bahan organik dan unsur hara, maka sludge kering ini dapat digunakan sebagai pengganti pupuk, apabila digunakan dalam volume

Tantangan yang dihadapi pemerintah dalam menerapkan sistem Otonomi Daerah diantaranya (1) mentalitas aparat pemerintah yang belum berubah dari mindset sentral

Sebuah skripsi yang diajukan untuk memenuhi salah satu syarat memperoleh gelar Sarjana pada Fakultas Pendidikan Bahasa dan Seni.. © Meilyna

Penanganan ketergantungan game online dengan bantuan dari berbagai pihak terutama pihak sekolah memberikan kepercayaan kepada konselor sekolah atau guru BK untuk

As such, no assurance can be given as to the Statistical Information s accuracy, appropriateness or completeness in any particular context, nor as to whether the