BIOL 456 Microbe-Microbe Symbiosis Pt. 1

Metabolic exchange

Microbes may benefit other microbial species by : ________

• Examples:

• Organic carbon

• Removing harmful waste

products

Commensalism

Example:

Cross Feeding -one organism benefits, the other not effected

Mutualism

Example:

Syntrophic metabolism – Both partners reliant on each other

Parisitism

Example:

• Ectoparasites: -one organism benefits, the other is harmed

Intraspecies Communication: Quorum Sensing

Regulation of gene expression in response to levels of diffusible signal molecules

bacterial population density

Intraspecies Communication: Quorum Sensing

• Abundance of signal molecules usually correlates with ________

autoinducers

Intraspecies Communication: Quorum Sensing

Various chemical signal molecules or _______ are used by different bacteria

quorum-sensing

Intraspecies Communication: Quorum Sensing

Both Gram-negative and Gram-positive bacteria use _________, but each use different chemicals

Intraspecies Signaling

• Microorganism can sense and respond to the presence of other microbial species

• Changes in gene expression allow for facultative symbioses

Intraspecies Signaling

Intraspecies Communication: Quorum Sensing

Cross-Feeding

A.k.a. reciprocal feeding or metabolic exchange

Cross-Feeding

One species produces metabolic byproducts that serve as nutrients or energy sources for another species.

facultative

Cross-Feeding:

Can be ________, meaning the interacting microbes do not always depend on each other for survival.

obligate or facultative

Cross-Feeding:

Key Features:

• Can be _________, depending on the dependency of each species on the exchanged metabolites.

bioreactors

Cross-Feeding:

Key Features:

Occurs in a variety of ecosystems, including soil, the human gut microbiome, and _______.

community stability and diversity

Cross-Feeding:

Key Features:

Drives microbial ___________ by enabling resource partitioning.

Syntrophic Metabolism

• Mutualistic interaction between two or more microbial species

• Each partner relies on the metabolic activity of the other

metabolic intermediates

Syntrophic Metabolism:

Often involves the interspecies transfer of _______, such as hydrogen (H2), formate, or acetate, which must be rapidly consumed to maintain favorable reaction energetics.

obligate metabolic cooperation

Syntrophic Metabolism:

Key Features:

• Involves __________ where neither partner can perform the reaction alone.

anaerobic environments

Syntrophic Metabolism:

Key Features:

Often observed in ________, such as sediments, wastewater treatment systems, and

the digestive tracts of animals.

propionate and acetate

Syntrophic Metabolism

Key Features:

Commonly occurs between ________ fermenting bacteria and methanogenic archaea,

where hydrogen-consuming methanogens enable the bacteria to continue fermentation.

Syntrophic Metabolism

• Archaeal methane oxidization occurs only in syntrophic consortia with bacteria performing anaerobic respiration

• Usually in marine systems

• Linked to the reduction of SO4^2-, NO3-, Fe^3+, and Mn4+

• Low energy yield

Anaerobic Decomposition

Three main processes:

• Fermentation

• Anaerobic Respiration

• Methanogenesis

consortium

Anaerobic Decomposition

Complete oxidation of carbon requires distinct microbial groups to work together as a _______

Anaerobic Metabolism: Fermentation

kind of a catch all term for metabolic processes that use an organic electron donor and an organic electron acceptor that is endogenous (produced within the cell)

often sugar

Anaerobic Metabolism: Fermentation

Substrates: ________

low molecular weight organic acids

Anaerobic Metabolism: Fermentation

Products: ____________, alcohols, H2, CO2

Anaerobic Metabolism: Anaerobic Respiration

Terminal electron acceptor is an inorganic compounds other than molecular oxygen (O2)

Denitrification

Anaerobic Metabolism: Anaerobic Respiration

NO3^- : _______

Iron Reduction

Anaerobic Metabolism: Anaerobic Respiration

Fe^+3 : _________

Manganese Reduction

Anaerobic Metabolism: Anaerobic Respiration

Mn^+4 : _________

Sulfate Reduction

Anaerobic Metabolism: Anaerobic Respiration

SO4^-2 : __________

Anaerobic Metabolism: Methanogenesis

• Biogenic production of methane (CH4)

• Performed by a few groups of Archaea

• Two major pathways

• Hydrogenotrophic

• H2 and CO2

• Acetoclastic

• Acetate

Division of labor

Benefits of Cross Feeding / Metabolic Exchange:

________:

• Can evolve to specialize and get highly efficient a given metabolism

specialized microenvironments

Benefits of Cross Feeding / Metabolic Exchange:

Allows for _________:

• e.g. Anaerobic microsites

Avoid biochemical conflict

Benefits of Cross Feeding / Metabolic Exchange:

__________:

• Compartmentalizes reactive intermediates

biosynthetic capacity

Benefits of Cross Feeding / Metabolic Exchange:

Greater _________

Secondary endosymbiosis

_________: the process of engulfing a green or red algal cell, retaining its chloroplast, and becoming phototrophic.

green algae

Secondary endosymbiosis:

Euglenids and Chlorarachniop hytes- _______

red algae

Secondary endosymbiosis:

Alveolates and Stramenopiles- ________

Algae

Not a taxonomic group

Defined as- Unicellular or filamentous photoautotrophs

Lacks roots, stems, and leaves

Is also mostly aquatic- water is necessary for growth and reproduction