Contributors and Sponsors

LSU students: Amanda Achberger W. Peyton Adkins Meggie Alleman Allen Bordelon Bethany Broekhoven Noelle Bryan Scott Burke Rongman Cai Sahiti Kilaru

Other collaborators: Sumeet Dua (LA Tech) Christine Foreman (Montana State) Laurence Henry (Southern University) Cindy Morris (INRA, Montfavet, France) Vaughan Phillips (University of Hawaii) Fred Rainey (Univ. Alaska-Anchorage) David Sands (Montana State) David Schmale (Virginia Tech) Mark Skidmore (Montana State)

LSU co-PIs and researchers: John Battista Brad Ellison Jim Giammanco T. Gregory Guzik Doug Granger Gary King Kevin McCarter Michael Stewart John Wefel

Cloudy with a chance of microbesLingering questions about the nature and role

of microorganisms in the atmosphere

Brent ChristnerDepartment of Biological Sciences, Louisiana State University

xner@lsu.edu

• Biological IN are the most active freeze catalysts in nature.

• Mineral dusts are not active as IN > -15oC, yet many clouds warmer than this contain ice phase precipitation.

• Biological IN may play a role in the processes leading to precipitation and Earth’s radiative balance.

• What is the high altitude boundary for life on Earth?

• Helium balloon payloads for the collection and microbial analysis of air samples from altitudes up to 38 km.

Total oversimplification of the processes leading to precipitation

Water vapor/droplets + ice nuclei + freezing temperature

Ice nucleation: deposition, condensation, contact, or immersion freezing(particles initiate the freezing of water vapor or droplets to form ice particles)

Ice crystal formation and growth(gain sufficient mass to overcome gravity and fall to the ground)

Snowflake formation orice melts and hits the ground as rain

Nucleating material oCKaolinite (clay mineral) -22Birch pollen -12Ice+ insects -6AgI -4.5Pantoea agglomerans ¥ -3Pseudomonas syringae ¥ -2

Warmest temperature of activity for some ice nucleation-active materials †

† Temperatures are for the immersion mode of ice nucleation ¥ The temperature of ice nucleation activity in Ice+ strains

Christner (2010) Appl Microbiol Biotech, 85:481-489

Determining the activity, quantity, and nature of freeze immersion ice nuclei or nucleators (IN)

e.g., ‘Untreated’ – ‘Lysozyme’ insensitive = # of bacterial IN

A. Achberger (unpublished data)

Montana France Antarctica and Yukon

IN active at -7oC in freshly collected snow from Montana, France, Antarctica, and the Yukon

~95% of the IN active at > -10oC in snow and rain are biological particles; at least 40% are bacterial in origin

Christner et al. (2008) Science, 319:1214;

PNAS, 48:18854-18859

Is there a bioprecipitation cycle?

Sands et al. (1982) J Hungarian Meteorol Serv 86:148-152; Morris et al. (2004) J Phys IV France, 121:87-103

Aerosolization of bacterial IN from the phylosphere

Ice nucleation in clouds and enhanced

precipitation

Epiphytic bacterial growth

Transfer of bacteria to new

plant host

In situ detection of biological particlesin cloud ice-crystals

• Sampled ice crystal residues while flying through clouds in the skies over Wyoming, USA.

• Used aircraft-aerosol time-of-flight spectrometry to directly measure the chemistry of individual cloud ice-crystal residues.

• Determined that ~50% of the ice-crystal residues were mineral dust; ~33% were biological particles.

• First evidence for the involvement of biological particles (i.e., bacteria, fungi and/or plant material) in ice-cloud processes.

(Pratt et al. 2009, Nature Geoscience, 2:398-401)

200 X

5 X

20 X

6 x108 km2 total leaf surface for

terrestrial plants(1024 to 1026 cells)

• Do biological IN possess the exclusive role as natural atmospheric IN at temperatures above about -15oC?

• Are their concentrations sufficient to trigger precipitation directly?

• Are unidentified biological particles active IN at lower temperatures?

• Are there large seasonal/regional variations of these types of IN?

• Can their numbers be defined and can they be identified by source?

Demott and Prenni (2010)

Direct measurements of biological IN are lacking for the full temperature regime relevant to ice formation in mixed-phase

clouds

Sampling microbes in the lower atmosphere using aerial unmanned autonomous vehicles (UAVs)

Above: A UAV fitted with 8 sampling surfaces that are shown in the open position. Sampling is controlled by remote control from the ground and it is possible to sample > 150,000 L of air during a single flight. Top right: Accurate sampling path (grey lines) of one of the UAVs flying around a single GPS waypoint (black dot) 100 m above the ground.

Images and video: David Schmale (Virginia Tech)

Video: HABITAT-1, July 2009; Image: HABITAT-5, June 2010

Aerobiological sampling using a latex sounding balloon platform

3000 g latex sounding balloon

Parachute

Cut down apparatus

Primary beacon

CW Morse Beacon

Secondary Beacon

Microbiological sampling payloads

A sounding balloon with < 5.4 kg of total payload is a low cost and logistically feasible approach to conduct microbiological sampling at altitudes in the troposphere and stratosphere.

Long duration sampling at 38 km with the High Altitude Student Payload (HASP)

Balloon Manufacturer Winzen

Balloon Type Zero pressure, 1 cap(W11.82-1E-37 CSBF #979)

Balloon Size  11.82 million cubic feet

Parachute Diameter 79 feet

HASP Weight 411 pounds

SIP Weight 589 pounds

Balloon Systems 458 pounds

Ballast 542 pounds

Altitude with Ballast 122,500 feet

Altitude without Ballast 126,000 feet

Ballast for Drive-Up 140 pounds

Ballast for Sunset 259 pounds

100 km

0

1000

2000

3000

4000

5000

6000

Laboratory control

Payload control

Payload sample

DN

A-c

onta

inin

g ce

lls p

er s

ampl

e10 mm

Determining the limits for microbial survival in the high atmosphere will…

• yield data to assess the geographic boundaries for microbial dispersal via the atmosphere on a global scale.

• reveal the properties of microbes surviving extremes of low pressure, temperature, and relative humidity and high fluence rates of UV.

• provide information that can be applied to assess the habitability of other planetary environments.

MARSLIFE: Modes of Adaptation, Resistance, and Survival for Life Inhabiting a Freeze-dried-radiation-bathed Environment (2010 NASA / LA BOR grant) 

At an altitude of 30 km, the pressure, temperature, and radiation levels are similar to the surface of Mars.

≈

Altitude (m

i)

Alti

tude

(km

)

Volume (m3) # of microbes Metric tons of carbonTroposphere (up to 17 km)

4 x 1018 4 to 40 x 1022 400 to 4000 †

Stratosphere (up to 50 km)

8 x 1018 1021 ? 20 ?

† Weight equivalent of 4 to 40 blue whales

“If I could have sampled at 1000 m above the ground with a balloon, the air would have been perfectly sterile.”Louis Pasteur (circa 1860)

Summary• Affect of biological IN on climate? A game of numbers.

• The role of biological IN in precipitation generation could be most relevant in clouds at temperatures > -15oC.

• Collaborative research needed between atmospheric scientists and microbiologists to quantify and characterize the ecological sources and meteorological role of biological IN.

• Species with characteristics (e.g., resistance to desiccation, cold, and UV/ionizing radiation) that provide a selective advantage in the atmosphere are relevant to astrobiology.

• The high altitude limits for life on Earth will provide information to assess the habitability of other planetary environments.