Hello Topknot,
How does light affect the way bacteria grows?
Few bacteria actually require light for growth. Pathogenic
bacteria, (Those that cause disease in humans, animals and plants) do
not require light to survive, but can be destroyed by UV light. (More
further down in the answer) Photosynthetic bacteria are comprised of
green and purple bacteria, and use light to photosynthesize their
food. This type of organism lives in the environment, primarily water.
?The most common environmental conditions that a microbiologist
considers are temperature, pH, oxygen, light, salt/sugar concentration
and special nutrients. Each bacteria has an optimum range of these
conditions within which it grows at a maximum rate.?
http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/Chap4.html#Environment
?Energy source:
Phototrophs (def) use radiant energy (light) as their primary energy source.
Combining their nutritional patterns, all organisms in nature can be
placed into one of four separate groups: photoautotrophs,
photoheterotrophs, chemoautotrophs, and chemoheterotrophs.
1. Photoautotrophs (def) use light as an energy source and carbon
dioxide as their main carbon source. They include photosynthetic
bacteria (green sulfur bacteria, purple sulfur bacteria, and
cyanobacteria), algae, and green plants. Photoautotrophs transform
carbon dioxide and water into carbohydrates and oxygen gas through
photosynthesis (def).
Cyanobacteria, as well as algae and green plants, use hydrogen atoms
from water to reduce carbon dioxide to form carbohydrates, and during
this process oxygen gas is given off (an oxygenic process). Other
photosynthetic bacteria (the green sulfur bacteria and purple sulfur
bacteria) carry out an anoxygenic process, using sulfur, sulfur
compounds or hydrogen gas to reduce carbon dioxide and form organic
compounds.
2. Photoheterotrophs (def) use light as an energy source but cannot
convert carbon dioxide into energy. Instead they use organic compounds
(def) as a carbon source. They include the green nonsulfur bacteria
and the purple nonsulfur bacteria.
http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/metabolism/growth/factors.html
?PHOTOTROPHS. Traditionally, these organisms are thought of as
being autotrophs and lithotrophs, taking in carbon dioxide and
generating reducing power by the oxidation of water with the release
of oxygen. The classic "photosynthetic equation" we grew up with and
applied to trees and other plants is based on this. In place of water,
the purple and green sulfur bacteria substitute hydrogen sulfide (H2S)
or hydrogen (H2). In Bacteriology 102, we study the purple non-sulfur
bacteria, all of which are heterotrophs and organotrophs ? obtaining
carbon and reducing power at the expense of organic compounds.
(Autotrophic/lithotrophic growth similar to that of the purple sulfur
bacteria is an alternative for some bacteria in this group.) For
phototrophs in general, ATP is generated by photophosphorylation.?
http://www.jlindquist.net/generalmicro/102bactnut.html
The definition of bacteria that need light for survival :
?Bacteria that derive energy from light by the process of
photosynthesis. See also Oxyphotobacteria.
http://www.ndif.org/Terms/Photobacteria.html
?These organisms are of the greatest biological interest because
they do not perform plant photosynthesis, which is otherwise the
universal mechanism of photosynthesis in the living world from
blue-green algae to higher plants.
The photosynthesis of these bacteria is never accompanied by oxygen
production. Furthermore, the photosynthetic bacteria never contain
chlorophyll a that is widely associated with plant photosynthesis.
Instead each group of this bacteria contains its own characteristic
type of chlorophyll.?
http://www.ftns.wau.nl/prock/Research/Rene/Intro_Photobacteria.htm
The equation for photosynthesis of these bacteria:
--------------------------------------------------
The preceding equation can be made more general by substituting "A"
for the oxygen ("O") in the source of reducing power when it is
realized that compounds other than water can serve in that capacity
for certain other types of organisms:
CO2 + 2H2A = CH2O + H2O + 2A
For the purple and green sulfur bacteria, hydrogen sulfide is
utilized, and the equation is given thus:
CO2 + 2H2S = CH2O + H2O + 2S
http://www.splammo.net/bact102/102pnsb.html
How photosynthetic bacteria evolved:
?Years 2.1 to 2.6 Billion:
Some of the oxygen produced by photosynthetic bacteria was
absorbed (oxidized) by iron dissolved in Earth's oceans.
This produced an ancient rain of minute, 'rusty' particles to
accumulate on the bed of the ancient ocean floors that is found today
as bands of haematite in rock.
As molecular oxygen became abundant, a fraction underwent
continuous conversion into a tri-atomic form known as ozone (O3). The
ozone rose to form a layer in Earth's atmosphere which helps to
protect the planet's carbon-based life forms moving onto the land from
damage by the Sun 's ultraviolet radiation.
As photosynthetic bacteria prospered and spread, and higher forms
(the 'eukaryotes')developed, the concentration of oxygen in air and
water became abundant.
Free oxygen began to build up around the middle of the Proterozoic
Period -- around 1.8 billion years ago -- and made way for the
emergence of life as we know it today. This event created conditions
that were toxic for most organisms present and thus made way for the
more oxygen dependent life forms to flourish and take over.
This heralded the start of the Cambrian Period began, about 550
million years ago. During this period, life "exploded," developing
almost all of the major groups of plants and animals in a relatively
short time.?
http://www.ozh2o.com/h2origin4.html
List of photosynthetic bacteria and a few short videos can be found here:
http://www-micro.msb.le.ac.uk/video/photosynthesis.html
?The abundance of life on Earth is almost entirely due to
biological photosynthesis, which depends on light energy. The source
of light in natural habitats has heretofore been thought to be the
sun, thus restricting photosynthesis to solar photic environments on
the surface of the Earth. If photosynthesis could take place in
geothermally illuminated environments, it would increase the diversity
of photosynthetic habitats both on Earth and on other worlds that have
been proposed to possibly harbor life. Green sulfur bacteria are
anaerobes that require light for growth by the oxidation of sulfur
compounds to reduce CO2 to organic carbon, and are capable of
photosynthetic growth at extremely low light intensities. We describe
the isolation and cultivation of a previously unknown green sulfur
bacterial species from a deep-sea hydrothermal vent, where the only
source of light is geothermal radiation that includes wavelengths
absorbed by photosynthetic pigments of this organism.?
http://www.pnas.org/cgi/content/abstract/0503674102v1
?Three decades ago, research on the biological effects of
ultraviolet light was stimulated by suggestions that supersonic
transport aircraft might destroy the ozone layer. The discovery of the
Antarctic ozone hole, however, was the real wake-up call. Many
scientists warned that increased UV-B levels were not only a threat to
species but might also disrupt ecosystems. One report on phytoplankton
(algae and other drifting plant life) in Antarctic waters showed a 6
to 12 percent decrease in their productivity--that is, conversion of
energy into biological mass through photosynthesis. This boded ill,
because phytoplankton are considered the base of the marine food web,
ultimately supporting such high-level consumers as fish, squid, and
whales.?
http://www.findarticles.com/p/articles/mi_m1134/is_6_110/ai_76550326
?CULLEN: "A concern that exists and remains is that some species of
phytoplankton might be affected more by UV radiation than others and
the potential exists that increased UV from ozone depletion might
alter species composition of phytoplankton in the Antarctic. Going up
the food chain there is a certain amount of research that's been done
looking at the effects of other organisms in the ocean, including the
bacteria that process food in the ocean, that help to recycle food,
and also the larval stages of fish and eggs. We know that UV radiation
affects the DNA of these organisms and can interfere with their
reproduction and survival."?
http://www.uaf.edu/seagrant/NewsMedia/97ASJ/07.15.97_OzoneHoles.html
UV light as a disinfectant:
?The ultraviolet component of sunlight is the main reason microbes die
in the outdoor air. The die-off rate in the outdoors varies from one
pathogen to another, but can be anywhere from a few seconds to a few
minutes for a 90-99% kill of viruses or contagious bacteria. Spores,
and some environmental bacteria, tend to be resistant and can survive
much longer exposures. UVGI systems typically use much more
concentrated levels of ultraviolet energy than are found in sunlight.?
http://www.engr.psu.edu/ae/iec/abe/control/ultraviolet.asp
?Ultraviolet radiation in the range 225?302 nm is lethal to
microorganisms and is referred to as ultraviolet germicidal
irradiation (UVGI).?
?The rate constant defines the sensitivity of a microorganism to UV
exposure and is unique to each microbial species. Most published test
results provide an overall rate constant that applies only at the test
intensity.?
Page 3 lists the rate necessary for certain types of organisms.
http://www.engr.psu.edu/ae/iec/abe/publications/math_modeling.pdf
Escherichia coli (E. coli) and Serratia marcescens were the bacteria
used in a study of the effects of light on organisms. Exposure to UV
light destroyed some bacteria:
?After incubation, bacteria on the side not exposed to ultraviolet
light (the shielded side) were observed to have grown into distinct,
visible colonies. None of the bacteria exposed to ultraviolet light
for two, five, or 30 minutes at 254 nm survived.
When the experiment was repeated, bacteria mortality was approximately
40-75% for Serratia marcescens exposed to ultraviolet light (at 254
nm) for 15 seconds and about 75-90% bacteria mortality for the 30
second exposure. One minute of exposure time to ultraviolet light
resulted in 95-99% bacteria mortality.
Therefore, complete mortality for Serratia marcescens is probably a
little longer than one minute, but less than two minutes.
Conclusions/Discussion
Ultraviolet light exposure for short time periods, such as two or five
minutes, was not expected to completely destroy the bacteria.
Similarly, it was not expected that bacteria exposed to ultraviolet
light (254 nm) for one minute would result in almost complete
mortality. Surprisingly, very low exposure times, such as 15 and 30
seconds resulted in at least 40% bacteria mortality and bacteria
exposed to 254 nm for one minute resulted in at least 95% mortality.?
http://www.usc.edu/CSSF/History/2004/Projects/J1303.pdf
?Question - Why are some bacteria more resistant to UV light? What
kind of specific experiments would determine uv resistantance?
-----------------
UV light can cause "spelling errors" in the DNA. Many organisms have
DNA repair mechanisms that help correct these errors. Think of it as
kind of a molecular "spell check." Some bacteria have these spell
checker and some don't. You and I also have these repair mechanisms.
There are some people who don't have the ability to repair these
mistakes and they are much more susceptible to cancer than someone
with normal repair mechanisms. You can use a UV lamp to shine light on
different kinds of bacteria for varying amounts of time to determine
how resistant they are. Be very careful when using UV light however,
it can damage your skin and eyes. Make sure you have an adult help
you.?
http://www.newton.dep.anl.gov/askasci/mole00/mole00471.htm
?Ultraviolet triggers the formation of peptide bonds between certain
amino acids in the pathogens' DNA molecules, which robs them of the
ability to reproduce and renders them harmless. As a result, UV is
known to be an effective disinfectant due to its strong germicidal
ability. UV light rays strike and destroy viruses, bacteria, fungi,
and pollen along with other microorganisms.?
http://www.thstore.com/thstore/technologies_2_Ultraviolet.asp
?These studies have shown that pulsed light emissions can
significantly reduce populations of E. coli 0157:H7 and L.
monocytogenes on exposed surfaces with exposure times which are 4-6
orders of magnitude lower than those required using continuous u.v.
light sources.?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9750325&dopt=Abstract
?Shortwave UV light can kill bacteria, irritate human eyes, and cause
a strong sunburn effect on skin (Wain, 1965). Shortwave UV light is
harmful to humans and all living things because it has the power to
change DNA. The energy in UV light, which is absorbed by DNA, can
actually break bonds in DNA?
http://www.geocities.com/tiffywiffyuva/Introduc.htm
?Water is passed through a disinfecting chamber containing a quartz
mercury lamp that emits ultraviolet light rays. The ultraviolet
irradiation kills or inactivates microorganisms almost instantly.
Ultraviolet light is a very effective disinfectant. However,
disinfection only occurs inside the unit. No residual disinfectant is
retained in the water to continue to kill bacteria that may be
introduced into the water after it is disinfected.
The major differences in UV units are the capacity and optional
features. Some units are equipped with UV detectors to warn the user
when the unit is dirty or the light source is failing. These detectors
must be properly calibrated and should not take the place of annual
light source replacement and regular cleaning.?
http://ohioline.osu.edu/b795/b795_9.html
Amount of light required to kill some organisms
http://www.maxmax.com/aUVGermicidalTechnicalData.htm
I hope this is the answer you were seeking. If not, please request an
Answer Clarification. I will be happy to assist you further, before
you rate this answer.
Regards, Crabcakes
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