Bacterial MVPS and Related Bacteria

Bacterial MVPS

Overview of Bacteria Classification

  • Proteobacteria

    • Major groups include:

    • Alpha-proteobacteria

    • Beta-proteobacteria (Purple sulfur bacteria)

    • Gamma-proteobacteria (C1-eaters, notably Pseudomonads)

    • Delta-proteobacteria (Nitrifiers, N2-fixers)

    • Epsilon-proteobacteria (Enterics)

  • Firmicutes (Gram-positive, categorized by sporulation):

    • Non-sporulating: Firmicutes (G+ve, no spores)

    • Sporulating: Firmicutes (G+ve, spores)

  • Actinobacteria (high GC Gram-positive bacteria)

  • Cyanobacteria

Proteobacteria Details

Characteristics

  • Diversity: Metabolically diverse across various environments, including chemoorganotrophs, chemolithotrophs, and phototrophs.

  • Phylogenetic Groups: Classified into five main groups: Alpha (α), Beta (β), Gamma (γ), Delta (δ), and Epsilon (ε) Proteobacteria.

  • Relation to Mitochondria: Many proteobacteria share genetic and metabolic similarities with mitochondria, fortifying theories of endosymbiosis.

Common Genera

  • Examples of genera in each subgroup:

    • Alpha: Rhizobium, Agrobacterium

    • Beta: Nitrosomonas, Neisseria

    • Gamma: Escherichia, Salmonella, Pseudomonas, Vibrio

    • Delta: Bdellovibrio, Desulfovibrio

    • Epsilon: Heliobacter

Purple Bacteria

Functionality

  • Anoxygenic Photosynthesis: Inhibited by O2, using H2S as an electron donor to convert CO2; contains unique bacteriochlorophylls which absorb specific light wavelengths.

  • Purple Sulfur Bacteria: Utilize H2S in anoxic environments to conduct photosynthesis, forming blooms in low oxygen lakes.

  • Winogradsky Column: Utilized for cultivating and studying anaerobic bacteria using carbon sources like newspaper or egg shells to simulate natural settings. Developed by Sergei Winogradsky in the 1880s.

Methylotrophs and Methanotrophs

Definitions & Characteristics

  • Methylotrophs:

    • Microorganisms that use C1 compounds (such as CH4, CH2OH, HCOOH) as their carbon source, distinguishing them as non-C-C bonded compounds.

  • Methanotrophs: A subset of methylotrophs able to use methane (CH4) specifically, utilizing methane monooxygenase (MMO) to convert methane to methanol.

    • These organisms are obligate aerobes and often found in environments rich in methane, often at the interface of oxic and anoxic zones (e.g., thermocline regions in lakes).

Nitrifiers

Functionality and Classification

  • Nitrifiers: Microorganisms that oxidize specific nitrogen compounds and contribute to the nitrogen cycle.

    • Include ammonia oxidizers (e.g. Nitrosomonas) and nitrite oxidizers (e.g. Nitrobacter, Nitrospira).

  • Use ammonia as an energy source, performing chemolithoautotrophic metabolism.

  • Ammonia Monooxygenase: A key enzyme in ammonia oxidation.

Enteric Bacteria

Characteristics

  • Found within the Gammaproteobacteria class, including notable genera such as Escherichia coli and Salmonella.

  • Typically facultative anaerobes with diagnostic characteristics (oxidase negative and peritrichous flagella)

  • Coliforms: A subgroup that are gram-negative, non-spore-forming, lactic acid fermenters associated with fecal contamination.

    • Serve as indicators for pathogenic bacteria in water quality assessments.

Agrobacterium and Rhizobia

Functions and Relationships

  • Members of the Alphaproteobacteria known for their symbiotic relationships with plants.

  • Agrobacterium: Known for causing crown-gall disease, transferring T-DNA into plant genomes via a Ti plasmid.

    • Involves complex interactions that lead to plant tumor formation and co-dependence of nutrient flows (e.g., nitrogen for carbon compounds).

Firmicutes Overview

  • Includes both spore-forming and non-spore-forming species. Characterized by a thicker peptidoglycan layer typical of Gram-positive bacteria.

Key Genera and Pathogens

  • Non-Sporulating:

    • Example: Staphylococcus (e.g., known to cause skin infections)

  • Sporulating:

    • Example: Bacillus (known for producing antibiotics and insecticidal toxins, such as Bacillus thuringiensis).

    • Example: Clostridium (anaerobic, some species are pathogenic such as Clostridium botulinum).