Bioprecipitation is the concept of rain-making
bacteria and was proposed by David Sands from
Montana State University
Montana State University (MSU) is a Public university, public land-grant university, land-grant research university in Bozeman, Montana. It is the state's largest university. MSU offers baccalaureate degrees in 60 fields, master's degrees in 6 ...
in 1982. The formation of
ice in
clouds is required for
snow and most
rainfall.
Dust and
soot particles can serve as
ice nuclei, but biological ice nuclei are capable of
catalyzing freezing at much warmer temperatures.
The ice-nucleating bacteria currently known are mostly
plant pathogens
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...
. Recent research suggests that bacteria may be present in clouds as part of an
evolved process of
dispersal.
Ice-nucleating proteins derived from ice-nucleating bacteria are used for
snowmaking.
Plant pathogens
Most known ice-nucleating bacteria are plant pathogens. These pathogens can cause freezing injury in plants. In the
United States alone, it has been estimated that
frost
Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...
accounts for approximately $1 billion in
crop damage each year. The
ice-minus variant of ''
P. syringae'' is a
mutant, lacking the
gene responsible for ice-nucleating surface
protein production. This lack of surface protein provides a less favorable environment for ice formation. Both
strains of P. syringae occur naturally, but
recombinant DNA technology
Molecular cloning is a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms. The use of the word ''cloning'' refers to the fact that the metho ...
has allowed for the synthetic removal or alteration of specific genes, enabling the creation of the ice-minus strain. The introduction of an ice-minus strain of P. syringae to the surface of plants would incur competition between the strains. Should the ice-minus strain win out, the ice nucleate provided by P. syringae would no longer be present, lowering the level of frost development on plant surfaces at normal water freezing temperature (0°C).
Dispersal of bacteria through rainfall
Bacteria present in clouds may have evolved to use rainfall as a means of dispersing themselves. The bacteria are found in snow,
soils and
seedlings in locations such as
Antarctica, the
Yukon Territory of Canada and the
French Alps, according to Brent Christner, a microbiologist at
Louisiana State University. It has been suggested that the bacteria are part of a constant
feedback
Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled ...
between terrestrial
ecosystems and clouds. They may rely on the rainfall to spread to new
habitats, in much the same way as plants rely on windblown
pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
grains, Christner said, with this possibly a key element of the bacterial life cycle.
Snowmaking
Many
ski resorts use a commercially available
freeze-dried preparation of ice-nucleating proteins derived from the bacterium species
Pseudomonas syringae to make snow in a snowgun.
See also
*
Pseudomonas syringae
*
Ice-minus bacteria
Ice-minus bacteria is a common name given to a variant of the common bacterium ''Pseudomonas syringae'' (''P. syringae''). This strain of ''P. syringae'' lacks the ability to produce a certain surface protein, usually found on wild-type ''P. syrin ...
*
Aeroplankton
References
{{reflist, 2
Bacteria
Weather modification