Building Ecology: Linking Microbial Ecology with Indoor Environment

and Building Science

Hal LevinBuilding Ecology Research Group

Santa Cruz, Californiahal.levin@buildingecology.com

EHEC serotype O104 E. coli -- 93 percent sequence similarity with the EAEC 55989 E. coli strain

Purpose of Presentation

• Summarize preliminary findings and questions re: IE factors relevant to microbial ecology of the indoor environment

• Stimulate discussion: what matters and why?

• Ask better questions for future research• Stimulate potential collaboration

between IE scientists and microbial ecologists

• Identify subjects for microBEnet workshops, valuable pilot studies

This is Bacillus subtilis, a ubiquitous bacterium whose spores are commonly found in house dust! On the left, the image of a colony grown on semi solid (agar) medium. On the right, a floating biofilm we call pellicle. Notice the complex architecture, wrinkles, ridges, aerial projections, etc.

Implications• A preliminary review of the

scientific literature related to environmental factors that affect the indoor microbial ecology suggests the existence of an extremely complex system.

• Future research will more comprehensively address indoor environmental microbial ecology with advanced gene-based tools.

• This review identifies important factors determining the microbial species present in the indoor environment.

The pellicles are remarkably robust… a penny thrown in does not break them…..

What is Building Ecology?

• Buildings = more than inanimate physical entities, masses of inert material that remain relatively stable over time.

• The building, what’s in it (occupants and contents), and what’s around it (the larger environment) – a interactive triad , all elements affect each other.

• Buildings = dynamic combination of physical, chemical, and biological dimensions. • Buildings can (must?) be described and understood as complex systems. • Microbial ecology of the indoor environment illustrates the complexity.• Models, methods, and tools similar to those used by ecologists to understand

ecosystems can help us understand the processes occurring out of sight, within the walls, and how those processes affect the durability and function of the building

The field of “microbial ecology” …

• Seeks to understand how microbes interact with other organisms (including both macroorganisms and other microbes) and with the environment.

• Like any other environment, buildings and other man-made objects provide rich habitats for microbes.

• Buildings provide space and nutrients for microbes, and the people (and various animals and plants) passing through continually carry new species to the community.

What is Microbial Ecology?

• Highly diverse activities from genetics to evolution to ecology• Ecologists looking at microbial communities in a wide range of

locations, from deep ocean to tropical forests to • Microbiologists using new genomic methods• Metagenomics: (who’s there and what are they doing?)– Built environment:

• Buildings houses (Moschandreas et al)• Urban environment

– Diverse “natural” locations • Tropical forests• Oceans: surface, deep vents, etc.

What can microbial ecologists do in the indoor environment?

• Identify the organisms or groups from which the organisms come

• Identify the conditions that give rise to the organisms found

• Identify the relationships or connections among the organisms or between organisms and environmental factors

• Help us predict what microbes will be found based on IEQ factors

What can building scientists do to help the microbial ecologists?

Carefully and thoroughly characterize the indoor environmental factors thought to be relevant to the microbes that are present.

Identify mechanisms of interactions between environmental factors and microbial ecology

Purpose and Summary

• Microbial ecologists characterizing indoor microbial ecology. • Sloan Foundation funding microbiologists, bioinformaticians,

microbial ecologists, and indoor and building scientists to advance understanding of the indoor microbial ecology.

• Simultaneous characterization of microbial ecology and associated indoor environmental factors will enable advances in both fields.

• Challenging to identify all relevant factors before more extensive, collaborative research.

• This presentation reviews preliminary efforts to identify the significant IE factors.

• Purpose: inform and stimulate discussions and collaboration among scientists working in the relevant fields.

Microbial ecology is diverse

• Genomes to human systems to ecosystems• Human microbiomes to global environmental

systems• Characterizing abundance, diversity, evolution• Potential for prediction from indoor environmental

characteristics• Is reverse prediction possible?: microbes to indoor

environmental conditions

Focus of work to date

• Attempt to find literature connecting environmental conditions, especially indoors, and the microbes found there

• Sort through the diverse and abundant literature to identify prominent environmental factors as determinants of the microbial ecology of the indoor environment

Biofilm of a fluorecently tagged Bacillus subtilis on the root of a tomato plant, keeping it growing well and keeping pathogens at bay.

Level 1 – strong connection hypothesized based on abundant evidence in the scientific literature:

• Humidity: – Air: relative and absolute: for viruses, possibly as it contributes to vapor pressure– Surfaces: water activity as a function of air and material moisture content and

temperatures.• Temperature: surface and air• Ventilation (outdoor air change rate and room air distribution or air flow

patterns)• Surfaces of building materials (and furnishings) facing the enclosed space

and in the structure• Chemicals and materials found primarily on surfaces but also in air (dust,

organic matter, nutrients, biocides, others)• pH of moisture on surfaces: contribution of airborne chemicals (including

CO2) to surface moisture Ph• People (age, size/activity/metabolic rate, culture)

Level 2–Important building components or processes w/ plausible connections, but either not strong or not well-established

• Filtration • Cleaning practices• HVAC system

– System type– Humidity in HVAC systems (Water blowing off coils, accumulated in drip pans, etc.) – Air conditioning (yes or no)– Humidifiers– UVc on wetted surfaces – Extent of drainage of water from HVAC surfaces

• Envelope design and construction quality• Maintenance (building and HVAC) including frequency, materials and processes used• Type of materials used (e.g., plaster, vs. gypsum board, vs. the new mold-resistant

gypsum board)• Flat vs pitched roofs – important as a function of prevalence of precipitation• Roof overhangs versus none• Operable windows vs. sealed and occupant window- opening behaviors. • Toilets as a source of microbial agents• Organic compounds comprising the dust in duct work (or on building surfaces)

Level 3 – Additional factors that may affect the microbial ecology of the indoor environment

• Building location:– Biogeographical, e.g., latitudes, climates, historical factors (changes over time, past microbial

populations and their evolution) – Climate factors: latitude: some fungi only appear to occur at certain latitudes, effects of

severe storms, floods, weather cycles– Locality (as in adjacency to parks/natural areas/water bodies affecting what gets brought into

a building - indoor/outdoor transport factors)• Building type (e.g. hospitals different from residences - this relates to human

activities/building program)• Building design (overhangs, roofs, windows, etc. - and what about insulation? made a

big difference in the condensation in my apartment!)• Building materials/furnishings: I came across the terms 'substrates' and 'nutrients'• Room types/activities (kitchens, bathrooms different from office, bedroom) - the

word 'eco-niche' was in one of the articles relating to bathrooms, I think• Light / darkness, Ultraviolet light• Potential effects of interactions of other air pollutants• Pets, house plants• Smoking behavior

Examples of dynamic, interactive and independent processes

• Symbiosis between humans and gut flora

• Temperature and humidity and emissions of chemicals from building materials, furnishings, and consumer products

I give you this as a reminder of the fact that in a very healthy pastoral state, a foundational aspect (keystone) is the colonization of all surfaces by microbes: the root of the grass, the grass leaves, the fur on the sheep, their teeth, tongues and of course, the entrie surface of the intestinal tract. Same with us….

Endosymbiotic origin of eukaryotes

Creg Darby: Micro 202, June 4, 2007

All microbes are not bad!Animal- microbe mutualisms

Source: Creg Darby: Micro 202, June 4, 2007

Identify the “Patterns that Connect”Bateson, Mind and Nature: A Necessary Unity

ENVIRONMENT

PEOPLE

BUILDINGSMICROBES

Think you very much!

www.microBE.net

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