Distribution of Micorganisms in the Environment

1. Temperature

2. pH

3. Moisture

4. Nutrient availability

5. Oxygen

6. Salinity and pressure

Factors Affecting Distribution

Temperature

Influences enzyme activity, metabolism, and growth

pH

Determines whether microorganisms can tolerate acidic, neutral, or alkaline conditions

Moisture

Provide water necessary for cellular process

Nutrient availability

Determines the resources available for growth

Oxygen

Influences the distribution of aerobic and anaerobic microorganisms

Salinity and pressure

Affect microbial survival in aquatic and extreme environments

Lithosphere

• It is the Earth’s rigid outer layer, consisting of the crust and the brittle uppermost portion of the mantle

• It lies beneath the atmosphere and above the asthenosphere, which is another layer of the upper mantle

1. Bacteria

2. Fungi

3. Archaea

4. Protozoa

5. Cyanobacteria

Microorganisms in soil:

Bacteria

Decompose organic matter and participate in nutrient cycling

Fungi

Break down complex organic material, including cellulose and lignin

Archaea

Participate in processes such as ammonia oxidation

Cyanobacteria

Perform photosynthesis in suitable soil environments

1. Soil depth

2. Moisture

3. pH

4. Root exudates

5. Soil composition

Factors affecting microbial distribution in soil:

Hydrosphere

• The total amount of water on a planet

• Includes water that is on the surface of the planet, underground and in air

Hydro-ecosphere

• includes freshwater, marine water, groundwater, and aquatic sediments

• Microorganisms occur freely in water or attached to submerged surfaces

Aquatic microbial communities

• They vary according to light, temperature, salinity, pressure, and nutrient availability

• They contribute to primary production, decomposition, and nutrient cycling

Bacteria

The most numerous cellular organisms in water columns and bottom sediments

Archaea

Once thought to only live in extreme environment; make u roughly 40% of the ocean’s microbial life

Protists

Single-celled eukaryotic organisms that possess a nucleus and specialized internal organs

Fungi

Microscopic aquatic fungi and yeasts acts as the primary “cleanup crew” of the hydrosphere

Viruses

The most abundant biological entities in the hydrosphere, numbering an estimated 10 ^ 30 in the oceans

Vibrio cholerae

Bacteria-causing cholera

Photobacterium phosphoreum

Lives in association with some marine animals and produces light that may aid camouflage and prey attraction

Pseudomonas species

Break down organic matter, recycling nutrients and supporting the marine carbon cycleh

Prochlorococcus and Synechococcus

Are photosynthetic cyanobacteria that contribute significantly to global oxygen production and form the base of marine food webs

Thaumarchaeota (Ammonia-oxidizing Archaea)

• convert ammonia intro nitrite, supporting the marine nitrogen cycle

• They are abundant in ocean waters

Euyarchaeota (Methanogenic Archaea)

They produce methane in oxygen-free marine sediments, contributing to the carbon cycle

Halophilic Archaea

• they thrive in hypersaline environments, such as salt ponds and lagoons

• Some use bacteriorhodopsin to capture light energy, contributing to the purple or reddish coloration of these habitats

Bacillus subtilis - Spore Formation

Produces resistant endospores that survive harsh atmospheric conditions and disperse to new environments

Micrococcus luteus - Desiccation Resistance

Survives dry conditions; protective pigments help reduce UV damage

Pseudomonas syringae - Ice Nucleation

Promotes ice formation in supercooled water droplets, potentially influencing cloud formation and precipitation through bioprecipitation

Fungal Spore Dispersal

• Aspergilus and Cladosporium release airborne spores that can trigger allergies

• Spores travel through air currents and colonize new environments

• Alternaria includes plant pathogens that can damage crops

Respiratory Viral Pathogens

• Influenza viruses and SARS-CoV-2 can spread through infectious respiratory particles, including aerosols and droplets

• Their survival in the air depends on factors such as humidity, temperature, sunlight, and UV exposure

Global dispersal

Resistant spores and cells travel through air currents to colonize new habitats

Pathogen transmision

Airborne viruses and pathogenic bacteria can spread infections between hosts

Allergen production

Fungal spores can trigger allergies and asthma, affecting human health

Atmospheric modulation

Ice-nucleating bacteria can promote ice formation in clouds and influence precipitation

Dormant survival

Some microbes remain inactive in the air until they reach environments with favorable conditions for growth

1. Human microbiota

2. Plant-associated microbes

3. Animal-associated microbes

4. Co-evolution and mutualism

5. Host health and development

Host-associated microorganisms:

Human microbiota

Microbial communities in the gut, skin, mouth, and respiratory tract that support health and protect against pathogens

Plant-associated microbes

Root symbionts, endophytes, and leaf-surface microbes that help plants obtain nutrient and tolerates stress

Animal-associated microbes

Microorganisms that aid digestion, provide defense against pathogens, and support animal health

Co-evolution and mutualism

Hosts and microbes evolve together, sometimes forming mutually beneficial relationships

Host heath and development

Microbes contribute to digestion, immunity, nutrient absorption, and normal development

Gut microbiota

• vitamin production: some gut bacteria, including certain strains of E. Coli, produce vitamin K

• Fiber digestion: Bacteriodes break down complex plant fibers that humans cannot digest alone

• Gut protection: beneficial bacteria, such as Lactobacillus, produce acids that help inhibit harmful microbes

• Disease association: Clostridioides difficile can cause severe diarrhea, particularly after antibiotic use disrupts the gut microbiota

Skin microbiota

• Pathogen protection: Staphylococcus, epidermis helps prevent harmful microbes from colonizing the skin

• Skin lipid metabolism: Cutibacterium acnes (formerly Propionibacterium acnes) metabolizes skin oils and may contribute to acne

• Environmental resistance: Micrococcus luteus tolerates dry conditions and other stresses on the skin

Oral microbiota

• Tooth decay: Streptococcus mutans produces acids that damage tooth enamel and contributes to cavities

• Biofilm formation: Actinomyces species help establish and maintain dental plaque by attaching to tooth surfaces

Respiratory Tract Microbiota

• Colonization: Streptococcus pneumoniae can live in the upper respiratory tract without causing symptoms

• Opportunistic infections: it can cause pneumonia, meningitis, and sepsis when conditions favor infection

• Risk factors: weakened immunity and viral respiratory infections can increase the risk of pneumococcal disease

Rhizobium

forms root nodules in legumes and converts atmospheric nitrogen into ammonia that plants can use

Frankia

Associates with plants such as alder trees, helping rease soil nitrogen availability

Glomus species

Form fungal networks around plant roots, improving phosphorus, improving phosphorus and water uptake in exchange for carbohydrates

Agrobacterium tumefaciens

Causes crown gall disease by transferring DNA from its Ti plasmid into plant cells. This mechanism is also used in genetic engineering

Pseudomonas fluorescens

Some strains produce antibiotics and antifungal compounds that suppress plant pathogens and promote healthy root growth

Ruminococcus and Fibrobacter

Break down cellulose in the rumen of cattle and other ruminants, helping them digest plant material

Methanobrevibacter

Produces methane during anaerobic digestion in the rumen

Buchnera (aphids)

Produces essential amino acids that are lacking in the aphids’ diet of plant sap

Trichonympha (termites)

A protist that helps termites digest cellulose from wood; it can also host bacteria involved in nitrogen metabolism

1. Commensals

2. Mutualists

3. Pathogens

4. Opportunists

Host-microbe interaction categories:

Commensals

• benefit from living on or in a host without significantly helping or harming it

• E.g.: Staphylococus epidermidis on human skin

Mutualists

• Both the host and microorganism benefit

• Eg.g.: Rhizobium fixes nitrogen for legumes and receives nutrients from the plant

Pathogens

• Cause disease through tissue invasion, toxin production, or disruption of host functions

• E.g.: Mycobacterium tuberculosis

Opportunists

• Usually harmless or controlled by the host but can cause disease when immunity is weakened or normal barriers are disrupted

• E.g.: Candida albicans can cause opportunistic infections