Chapter 7 - Microbial Growth

All organisms are composed of:

matter

Cells are ______% water

70

What 6 elements are cells composed of?

carbon, hydrogen. oxygen, phosphorous, sulfur, nitrogen

Nitrogen fixation

the reduction of N₂ → organic nitrogen

Which types of microbes perform nitrogen fixation?

aerobes or anaerobes

Autotrophs

use CO₂ (inorganic carbon) as a source for carbon; energy is acquired from other sources

Heterotrophs

use a variety of carbon sources; energy is acquired from organic molecules

What is the energy source for phototrophs?

light

What is the energy source for chemotrophs?

oxidation of chemical compounds

What is the energy source for lithotrophs?

reduced inorganic substances

What is the energy source for organotrophs?

electrons from organic compounds

Ectosymbiont

when an organism is located on the surface of another organism

Endosymbiont

When an organism is located within another organism

Symbiosis

an association of two or more different species of organisms

Symbiont

an organism that has a specific relationship with another that can be characterized as mutualism, parasitism, commensalism or amensalism

True or false: all ectosymbionts are positive.

False

True or false: not all endosymbionts are negative.

True

Microbial interaction

a type of relationship that affects fitness

Mutualism

an obligatory symbiotic relationship between two or more species where both parties benefit (+/+); its species fitness depends on the interaction

Cooperation

a non-obligatory symbiotic relationship between two species where both parties benefit (+/+); interaction is not species to species dependent for fitness

Commensalism

a symbiotic relationship where one party benefits while the other is not affected (+/0); can also involve the modification of the environment by one organism, making it more suited for another organism

Ammensalism

a type of interaction in which one species is harmed or inhibited, while the other species is unaffected (-/0); difficult to define in microbes

Predation

a type of interaction between species in which the predator survives by killing the prey (+/-)

True or false: predators are always at a lower trophic level than their prey.

False

Parasitism

a symbiotic relationship between two organisms in which one benefits while the other is harmed (+/-)

True or false: parasites often live exclusively on or in their host organism.

True

How is parasitism different from predation?

Parasites do not kill their hosts, while predators kill prey.

Niche

the interrelationship of a species with all the biotic and abiotic factors affecting it

Interspecific Competition

competition between members of a different species

Intraspecific Competition

competition between members of the same species

When does interspecific competition occur?

When two organism try to acquire or use the same resources

What are the outcomes of interspecific competition?

resource partitioning and competitive exclusion

Resource partitioning

when species reduce competition by reducing overlap in fundemental niches; occurs through niche differentiation

Niche differentiation

when natural selection selects against the individuals that compete with each other in an interspecies competition, causing the two species to develop different niches

Competitive Exclusion

occurs when two organism try other acquire or use the exact same resources (their niches overlap completely); one organism dominates and the other is driven to extinction

Red Queen Hypothesis

the idea that continuing adaptation is needed din order for a species to maintain its relative fitness amongst the systems it is co-evolving with

Biofilm

complex, permanently attached communities of prokaryotes; causes environmental problems or chronic bacterial infections in humans

What are the steps of biofilm formation?

1) Attachment, 2) Growth, 3) Maturation, 4) Detachment

Extracellular Polymeric Substance (EPS)

complex polymers secreted by microorganisms that are essential for biofilm formation and adhesion to surfaces

During the growth and maturation period of biofilm formation _______ and _______ occurs among microbial components when quorum sensing and the EPS is formed.

cooperation and mutualism

Why do biofilms pose a problem in medical fields?

they are difficult to treat as the biofilm is hard to penetrate; highly resistant to antibiotics; exhibit heterogeneity, complexity, and are dynamic in community composition of microorganisms

Quorum sensing

cell-cell communication mediated by small signaling moelules; plays an essential role in the regulation of gens who’s products are needed for the establishment of virulence, symbiosis, biofilm production, and morphological differentiation in a wide range of bacteria

Most bacterial and archaeal cells reproduce by______

binary fission

What are the phases of binary fission?

Growth period, chromosome replication and partitioning, cytokinesis

What poses the biggest complication for binary fission?

the cell wall

Septation

the formation of a cross wall between two daughter cells

What are the steps for septation?

selection of a site for the septum, assembly of a Z ring, assembly of cell wall synthesizing machinery, and the constriction of the cell and septum formation

Protein FtsZ

protein involved in binary fission that forms the Z ring, allowing for the division of the cell wall

The Z-ring links to the _______ of the cell during division

plasma membrane

Constriction of the _______ results in division.

Z-ring

Bacterial growth

refers to population growth; increases in cell number and cell size occurs

What are the phases of bacterial growth?

1) lag phase, 2) exponential phase, 3) stationary phase, 4) death phase, 5) long term stationary phase

Lag phase

phase in bacterial growth where the cell is synthesizing new components; varies in length; can be short or even absent

Exponential phase

phase in bacterial growth where the rate of growth and division is constant and maximal; nutrient availability is not limiting the population is out uniform in terms of chemical and physical properties; also referred to as log phase

Stationary phase

phase in bacterial growth where the closed system population growth eventually ceases; the total number of viable cells remains constant; active cells stop reproducing or reproductive rate is balanced by death rate; population may cease to divide but remain metabolically active

What are possible reasons for the stationary phase to occur?

nutrient limitation, limited oxygen availability, toxic waste accumulation, critical population density reached

Death phase

phase in bacterial growth where the number of viable cells declines exponentially; cells die at a constant rate rate due to detrimental environmental changes such as nutrient deprivation; the buildup of toxic wastes causes irreparable harm to the cells

Long-term stationary phase

phase in bacterial growth where successive waves of genetically distinct variants and natural selection occurs; the bacterial population continually evolves; does not occur of all populations

Doubling time

the time required for a population other than double in size; depends on species of microorganism and environmental conditions

Equation for calculating population size over time

Nf= (Ni) 2^n

Nf

total number of cells in the population

Ni

starting number of cells

n

generation time

2ⁿ

number of cells in that generation

What are environmental factors affecting bacterial growth rates?

temperature, oxygen concentrations, pH, osmotic pressure, barometric pressure, and radiation

True or false: microbes can regulate their internal temperatures.

False

How does temperature affect bacterial growth rates?

the enzymes they contain have functionally optimal temperature ranges

What are some adaptations that thermophiles have that let them exist in extreme temperatures

stabilized protein/enzyme structure (increased number of H bonds) and a membrane stabilized by more saturated, highly branched, and higher molecular weight lipids

How does oxygen concentration affect bacterial growth?

a microbe’s metabolic process can either benefit from or be hindered by oxygen; depends on the ETC and the terminal electron acceptor used

Aerobe

microorganism that grows in the presence of O₂

Obligate Aerobe

microorganism that requires O₂

Anaerobe

microorganism that grows in the absence of O₂

Obligate Anaerobe

microorganism that is usually killed in the presence of O₂

Microaerophile

requires 2-10% of O₂

Facultative Anaerobe

does not require O₂ but growns better in its presence

Aerotolerant Anaerobes

grows with or without O₂

Microorganism tend to maintain a ______ pH

neutral

How do microoganisms change the pH of their habitats?

by producing waste products

Acidophiles

actively pump out H⁺; growth optimum between pH 0-5.5 (acidic)

Most microbial fungi and archaeans are

acidophiles

Neutrophiles

exchange K for H⁺; growth optimum between pH 5.5-8 (neutral)

Most bacteria are

neutrophiles

Alkaliphiles

growth optimum between pH 8-11.5

Osmoregulation

the homeostatic mechanism by which bacterial cells maintain balance with the environment

microbes that live on land and water surface live at ______atm

1.0

Barotolerant

adversely affected by increased pressure, but not as severely as nontolerant organisms

Barophilic/peizophilic) organisms

require or grow more rapidly in the presence of increased pressure; changes membrane fatty acids to adapt to high pressures

How does radiation affect microorganisms?

causes mutations that indirectly result in death disrupts the chemical structure of many molecules such as DNA