Name: microbes and water availability in salty environments
Uploaded: 2025-06-12T09:41:47.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.b

factors-influencing-microbial-growth-osmolarity

Factors Influencing Microbial Growth: Osmolarity

Osmolarność to stężenie substancji rozpuszczonej wokół komórki, wpływające na dostępność wody. Gdy osmolarność wewnętrzna i zewnętrzna są zrównoważone, nie występuje ruch wody netto. Woda porusza się na zasadzie osmozy. W środowiskach o wysokiej zawartości substancji rozpuszczonych opuszcza komórki drobnoustrojów, powodując odwodnienie i zahamowanie wzrostu. Aktywność wody mierzy dostępność wody dla drobnoustrojów, zmniejszając się wraz ze wzrostem osmolarności. Większość drobnoustrojów wymaga aktywności wody powyżej 0,98, ale niektóre mogą przystosować się do niższych poziomów. Halofile rosną w słonym środowisku, zwykle od 3 do 15% chlorku sodu. Ekstremalne halofile, takie jak Halobacterium, potrzebują ponad 15% soli i najlepiej rosną między 20–30%. Drobnoustroje halotolerancyjne zazwyczaj tolerują od 0,1% do 10% soli. Osmofile rozwijają się w warunkach wysokiej zawartości cukru, w których dostępność wody jest ograniczona. Kserofile rozwijają się w ekstremalnie suchych warunkach, takich jak pustynie lub konserwowana żywność, gdzie aktywność wody jest minimalna. Aby przetrwać w ekstremalnych warunkach, drobnoustroje utrzymują równowagę osmotyczną poprzez aktywny transport substancji rozpuszczonych do komórki lub gromadzenie kompatybilnych substancji rozpuszczonych, takich jak betaina glicynowa lub trehaloza, w celu zatrzymania wody.

czynniki wpływające na wzrost drobnoustrojów: osmolalność

Osmolarno&#347;&#263; to miara st&#281;&#380;enia substancji rozpuszczonych w roztworze. Odgrywa ona kluczow&#261; rol&#281; w okre&#347;laniu dost&#281;pno&#347;ci wody dla organizm&#243;w. Woda przemieszcza si&#281; przez b&#322;ony p&#243;&#322;przepuszczalne na drodze osmozy &#8211; z obszar&#243;w o ni&#380;szym st&#281;&#380;eniu substancji rozpuszczonych (bardziej rozcie&#324;czonych) do obszar&#243;w o wy&#380;szym st&#281;&#380;eniu (bardziej st&#281;&#380;onych).
W &#347;rodowiskach o wysokim st&#281;&#380;eniu substancji rozpuszczonych kom&#243;rki drobnoustroj&#243;w trac&#261; wod&#281;, co prowadzi do ich odwodnienia i zahamowania wzrostu. Dost&#281;pno&#347;&#263; wody dla drobnoustroj&#243;w w takich warunkach wyra&#380;ana jest jako aktywno&#347;&#263; wody (a_w). Wraz ze wzrostem osmolarno&#347;ci aktywno&#347;&#263; wody maleje, a wi&#281;kszo&#347;&#263; drobnoustroj&#243;w wymaga minimalnej warto&#347;ci a_w powy&#380;ej 0,98, aby m&#243;c si&#281; rozwija&#263;.
Adaptacje drobnoustroj&#243;w do stresu osmotycznego
Drobnoustroje zasiedlaj&#261;ce &#347;rodowiska o niskiej aktywno&#347;ci wody wykazuj&#261; wyj&#261;tkowe zdolno&#347;ci adaptacyjne.
<ul>
<li>Halofile, na przyk&#322;ad, rozwijaj&#261; si&#281; w &#347;rodowiskach o wysokim st&#281;&#380;eniu soli i wymagaj&#261; st&#281;&#380;enia chlorku sodu w zakresie od 3 % do 15 % dla optymalnego wzrostu.</li>
<li>Ekstremalne halofile, takie jak Halobacterium, wymagaj&#261; jeszcze wy&#380;szego st&#281;&#380;enia soli &#8211; przekraczaj&#261;cego 15 % &#8211; aby podtrzyma&#263; aktywno&#347;&#263; metaboliczn&#261;.</li>
<li>Mikroorganizmy halotolerancyjne natomiast potrafi&#261; rosn&#261;&#263; w szerszym zakresie zasolenia, toleruj&#261;c st&#281;&#380;enia chlorku sodu od 0,1 % do 10 %.</li>
<li>W &#347;rodowiskach bogatych w cukier osmofile wykazuj&#261; wyspecjalizowane adaptacje umo&#380;liwiaj&#261;ce funkcjonowanie przy ograniczonej dost&#281;pno&#347;ci wody. Organizmy te powszechnie wyst&#281;puj&#261; w &#347;rodowiskach zasobnych w cukry, takich jak syropy i &#380;ywno&#347;&#263; zakonserwowana.</li>
<li>Kserofile z kolei s&#261; przystosowane do wyj&#261;tkowo suchych warunk&#243;w. Rozwijaj&#261; si&#281; w suchych ekosystemach, takich jak pustynie, oraz w &#347;rodowiskach, w kt&#243;rych techniki konserwacji &#380;ywno&#347;ci znacz&#261;co obni&#380;y&#322;y aktywno&#347;&#263; wody.</li>
</ul>
Mechanizmy utrzymywania r&#243;wnowagi osmotycznej
Aby przetrwa&#263; w tak ekstremalnych warunkach, drobnoustroje utrzymuj&#261; r&#243;wnowag&#281; osmotyczn&#261;, stosuj&#261;c dwie g&#322;&#243;wne strategie. Niekt&#243;re aktywnie transportuj&#261; do wn&#281;trza kom&#243;rki jony i inne substancje osmotycznie czynne, by zr&#243;wnowa&#380;y&#263; zewn&#281;trzn&#261; osmolarno&#347;&#263;, inne za&#347; gromadz&#261; tzw. kompatybilne rozpuszczalniki (ang. compatible solutes), takie jak betaina glicynowa i trehaloza. Zwi&#261;zki te nie zak&#322;&#243;caj&#261; proces&#243;w kom&#243;rkowych, ale pomagaj&#261; zatrzyma&#263; wod&#281; wewn&#261;trz kom&#243;rki. Takie adaptacje umo&#380;liwiaj&#261; drobnoustrojom przetrwanie i namna&#380;anie si&#281; w wymagaj&#261;cych &#347;rodowiskach, demonstruj&#261;c odporno&#347;&#263; &#380;ycia na ekstremalny stres osmotyczny.

Czynniki wpływające na wzrost drobnoustrojów: osmolalność

Osmolarno&#347;&#263; to miara st&#281;&#380;enia substancji rozpuszczonych w roztworze. Odgrywa ona kluczow&#261; rol&#281; w okre&#347;laniu ...

Education

JoVE Core

Microbiology

Mikrobiologia

Unit

Jednostka

Microbial Growth      

Wzrost drobnoustrojów

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

microbes and water availability in salty environments

Microbes and water availability in salty environments are closely linked to osmolarity, which is the measure of solute concentration in a solution. Osmolarity helps determine how much water is available for living things. Water moves across semipermeable membranes by osmosis. It flows from a more dilute area to a more concentrated one.

When the outside environment has a high solute level, microbial cells lose water. This can cause dehydration and slow or stop growth. The amount of water available to microbes is described by water activity, or aw. As osmolarity rises, water activity falls. Most microbes need an aw above 0.98 to grow.

Some microbes are adapted to low water activity conditions. Halophiles grow in high-salt environments and usually need sodium chloride levels between 3% and 15% for best growth. Extreme halophiles, such as Halobacterium, require salt levels above 15% to keep metabolism active. Halotolerant microbes can grow across a wider salt range, from 0.1% to 10% sodium chloride.

High sugar and dry habitats also create osmotic stress. Osmophiles live in sugar-rich places such as syrups and preserved foods. Xerophiles are adapted to very dry environments. They are found in deserts and in foods preserved so that water activity is very low.

Microbes use two main strategies to keep osmotic balance. Some actively transport solutes into the cell to match the outside environment. Others build up compatible solutes, such as glycine betaine and trehalose. These compounds help the cell hold water without disturbing normal cell processes. These adaptations let microbes survive and grow in harsh osmotic conditions.

Microbes and Water Availability in Salty Environments

microbes-and-water-availability-in-salty-environments

binary fission

Bacterial Cell Division by Binary Fission

Binary fission is the main way prokaryotes, such as bacteria, reproduce asexually. It produces two daughter cells that are genetically identical. When conditions are favorable, this process helps bacterial populations grow quickly. The process starts when the bacterial chromosome is copied. The circular DNA unwinds at a specific origin of replication called oriC. DNA polymerases then build matching strands in both directions until replication reaches the terminus. This creates two identical...

generation time

Bacterial Doubling Time

Bacterial generation time is the time needed for a bacterial population to double during exponential growth. It is a useful measure of microbial growth under optimal conditions. The rate can vary a lot from one species to another, and it can be affected by temperature, pH, and nutrient availability. Some bacteria grow quickly, while others grow much more slowly. Escherichia coli can have a generation time of about 20 minutes. Mycobacterium tuberculosis has a much longer doubling time, often 12...

bacterial growth curve

Stages of Bacterial Population Growth

Bacterial population growth in a closed system follows a set pattern called the bacterial growth curve. It describes how a bacterial population changes when temperature and nutrient levels are controlled. The curve has four phases: lag, log, stationary, and death. The lag phase is the first stage. During this time, bacteria adjust to their new environment. They make enzymes and other needed molecules for cell division, but the number of cells changes very little. This step prepares the...

microbial growth measurement: direct methods

microbial-growth-measurement-direct-methods

Counting Microbes with Direct Methods

Counting microbes with direct methods gives a fast way to measure how many cells are in a culture. In microbiology, these methods provide quantitative data for research and diagnostics. The main approaches are microscopic counts, plate counts, and serial dilution. Microscopic counting uses a Petroff-Hausser chamber, which is a special microscope slide with a grid and a known depth. A liquid culture is viewed under the microscope, and the cells in the grid are counted to estimate cell density...

microbial growth measurement: indirect methods

microbial-growth-measurement-indirect-methods

Measuring Microbial Growth Without Counting

Measuring microbial growth with indirect methods helps scientists estimate population size without counting every cell. These methods track signs of growth such as turbidity, metabolic activity, and biomass. They are useful because they are efficient and can give reproducible results. Turbidity is one common approach. During exponential growth, microbial cells scatter light in proportion to their biomass. A spectrophotometer measures this as optical density, or OD, also called absorbance.

microbial growth media

Selecting Microbial Growth Media

Microbial growth media give microorganisms the nutrients and conditions they need to grow in the lab. These media let scientists study microbial physiology, behavior, and interactions. Choosing the right medium is important for research, diagnosis, food safety, and environmental studies. Growth media can be solid, liquid, or semisolid. Solid media, often made with agar, support visible colony growth so microbes can be isolated and counted. Liquid media support even growth throughout the tube...

need for obtaining pure cultures

Isolating and Preserving Pure Cultures

Pure cultures are single microorganism species grown apart from mixed samples. They help scientists study microbes with the same genetic and physical traits under controlled conditions. This makes pure cultures important in microbiology research and in many real-world uses. To obtain a pure culture, a single microbial type must first be separated from a mixed population. Common methods include serial dilution, streak plating, pour plating, and spread plating. The chosen sample is then placed...

techniques for isolation of pure cultures

techniques-for-isolation-of-pure-cultures

Microbial Colony Isolation Methods

Microbial colony isolation methods are used to grow, separate, and count microorganisms in the laboratory. These techniques depend on placing microbes into a suitable growth medium under aseptic conditions, which help prevent contamination. The inoculum, or sample added to the medium, may be transferred directly or prepared as a diluted bacterial suspension. The streak-plate method is a common way to obtain pure microbial colonies. In this method, a sample is spread across the agar surface in...

factors influencing microbial growth: ph

Microbial pH Preferences and Growth Adaptation

Microbial growth depends on pH, the measure of how acidic or alkaline an environment is. Different microorganisms grow best in different pH ranges. Their ability to keep a stable internal pH helps protect enzymes and other macromolecules. External pH changes can challenge that balance. Neutrophiles grow best near neutral pH, usually between 5.5 and 8.0. Escherichia coli is a common example. These microbes often live in neutral or slightly acidic places. They can use potassium-proton exchange...

factors influencing microbial growth: temperature

factors-influencing-microbial-growth-temperature

Microbial Growth at Different Temperatures

Temperature shapes microbial growth by changing enzyme activity, membrane fluidity, and other cell processes. Each microorganism has a minimum, optimum, and maximum temperature range. Below the minimum, membranes lose fluidity and transport stops. Above the maximum, proteins denature and membranes break down. At the optimum temperature, enzyme reactions run fastest and growth is highest. Microorganisms are grouped by the temperatures they prefer. Psychrophiles grow in cold environments from...

factors influencing microbial growth: osmolarity

Microbes and water availability in salty environments are closely linked to osmolarity, which is the measure of solute concentration in a solution. Osmolarity helps determine how much water is available for living things. Water moves across semipermeable membranes by osmosis. It flows from a more dilute area to a more concentrated one. When the outside environment has a high solute level, microbial cells lose water. This can cause dehydration and slow or stop growth. The amount of water...

oxygen requirements and growth patterns

Microbial Oxygen Needs and Tolerance

Microbial oxygen needs and tolerance shape how bacteria grow and survive. Oxygen can support energy production in some microorganisms, but it can also become harmful in certain environments. These differences help explain why microbes live in very specific places. Microorganisms are grouped by how they use oxygen. Obligate aerobes, such as Mycobacterium tuberculosis, need oxygen because it serves as the terminal electron acceptor in aerobic respiration. Obligate anaerobes, such as Clostridium...

biofilms

Biofilm Growth and Surface Attachment

Biofilms are communities of microorganisms that attach to a surface and build a self-made sticky matrix around themselves. This matrix is made of extracellular polysaccharides, which are sugar-based substances secreted by the cells. Biofilms may contain one species or several species, and their organized layers help the microbes survive better together. Biofilm formation happens in four main stages: attachment, colonization, development, and dispersal. In the first stage, free-swimming...

key terms and concepts

Explore how osmolarity, water activity, and osmosis affect microbial growth in salty, sugary, and dry environments, including halophiles and xerophiles.

Microbes and Water Availability in Salty Environments | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Introduction to Virus

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Size and Structure of Viral Genomes

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Viral Replication: Lytic Cycle

Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized ...

Viral Replication: Lysogenic Cycle

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DNA Bacteriophages

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Viruses of Archaea

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Viruses with RNA Genomes

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CRISPR/Cas9 Genome Editing

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Subviral Agents

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The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  viruses depend on a host for metabolic processes;

BIO.4.a

Binary Fission

Binary fission is the primary mode of asexual reproduction in prokaryotes, such as bacteria. It results in the production of two genetically identical ...

Generation Time

Bacterial generation time, the period required for a bacterial population to double during its exponential growth phase, serves as a critical measure of ...

Bacterial Growth Curve

The bacterial growth curve is a fundamental concept in microbiology that describes the dynamics of bacterial population growth in a closed system with ...

Microbial Growth Measurement: Direct Methods

Direct methods for measuring microbial populations in a culture are essential tools in microbiology, providing quantitative data for various applications. ...

Microbial Growth Measurement: Indirect Methods

Estimating microbial growth is essential for understanding population dynamics and environmental adaptations. Indirect methods provide valuable insights ...

Microbial Growth Media

Microbial growth media are essential tools in microbiology, providing the nutrients and conditions necessary to cultivate and study microorganisms. These ...

Need for Obtaining Pure Cultures

Pure cultures, defined as the growth of a single microorganism species isolated from mixed populations, are fundamental tools in microbiological research ...

Techniques for Isolation of Pure Cultures

Microorganisms are routinely cultured in the laboratory using various techniques to isolate, grow, and quantify them for further study. These methods rely ...

Factors Influencing Microbial Growth: pH

Microorganisms are classified as acidophiles, neutrophiles, or alkaliphiles based on their pH growth preferences, reflecting their adaptations to specific ...

Factors Influencing Microbial Growth: Temperature

Microorganisms display remarkable adaptations, enabling them to thrive in diverse ecological niches across a wide range of temperatures. Temperature ...

Osmolarity is the measure of solute concentration in a solution. It plays a critical role in determining water availability for organisms. Water moves ...

Oxygen Requirements and Growth Patterns

Microorganisms exhibit diverse oxygen requirements and growth patterns driven by their metabolic strategies and environmental adaptations. Oxygen, while ...

Biofilms

Biofilms are complex communities of microorganisms encased in a self-produced extracellular polysaccharide matrix attached to surfaces. These microbial ...

The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include the modes of reproduction/replication can be compared

Prokaryotic vs. Eukaryotic Cells

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Microbial Morphologies 

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Bacterial Cell Wall 

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Archaeal Cell Wall

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Peptidoglycan Synthesis

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Plasma Membrane in Bacteria and Archaea

The plasma membrane is an essential cellular structure responsible for maintaining cellular integrity and regulating the selective transport of molecules. ...

Outer Layers of the Cell Envelope

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Flagella and Motility in Bacteria

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Fimbriae, Pili, and Axial Filaments

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Cell Inclusions

Prokaryotic cells possess a variety of inclusions that play crucial roles in nutrient storage, metabolic processes, and environmental adaptation. These ...

Endospores and Sporulation

Endospores are specialized, dormant cells primarily formed by Gram-positive bacteria, including Bacillus and Clostridium, enabling survival under extreme ...

Nucleoid

The nucleoid represents a structurally and functionally distinct region within prokaryotic cells, where the cell's DNA and associated proteins are housed. ...

Surface Appendages of Archaea

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The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  the structures and functions can be compared

BIO.4.c

Types of Microorganisms

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environmental-applications-of-microorganisms

Environmental Applications of Microorganisms

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Community DNA Extraction from Bacterial Colonies

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detecting-environmental-microorganisms-with-polymerase-chain-reaction

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Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
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Quantifying Environmental Microorganisms and Viruses Using qPCR

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Water Quality Analysis via Indicator Organisms

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Isolation of Fecal Bacteria from Water Samples by Filtration

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
The quality of water destined ...

detection-of-bacteriophages-in-environmental-samples

Detection of Bacteriophages in Environmental Samples

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Viruses are a unique group of ...

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Culturing and Enumerating Bacteria from Soil Samples

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bacterial-growth-curve-analysis-and-its-environmental-applications

Bacterial Growth Curve Analysis and its Environmental Applications

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
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Bacteria are among the most ...

The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  bacteria and viruses have a role in other organisms and the environment; and

BIO.4.d

History of Microbiology

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Infection

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Defense Mechanism Against Infection

Natural flora, body system defenses, and inflammation are natural barriers of the body against infectious agents regardless of previous exposure. Normal ...

The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  the germ theory of infectious disease is supported by evidence.

BIO.4.e

Microbes and Water Availability in Salty Environments

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