There are many reason the bacteria to produce pigments.

1. Phototsynthesis

2. UV protection

3. Defense mechanisms

4.Secondary metabolites for storage of energy

5. Stress

It varies with environment differs in marine, terrestrial and space.

Good luck

Some microbial pigments, including some carotenoids, have been demonstrated to increase tolerance to ultraviolet radiation.

This paper may be helpful!!

The tolerant to UV radiation is offten selective property for some microorganisms.. Thera are a lot of pigments, e.g. bacterial carotenoids, melanins, others.. Some pigment is typical for concreate kind of bacteria, e.g. prodigiosin - Serratia marcescens - production by 25-30 °C of cultivation.

Bacteria produce pigment for many reasons and it play avital role in photosynthesis as cyanobacteria or as actinorhodin like in the case of serratia marcescens

As allready mentioned pigments can have different function. In staphylococci pigmentation is intracellular and is regulated by the SOS stress response indicating a main function in UV tolerance. If you place a disk with ciprofloxacin on a plate streaked with Staphylococcus aureus you can observe a strong increase in pigmentation. Other bacteria produce pigments which at least in part leave the cell and can act as antimicrobial or signaling molecules. If you streak a half clear agar plate (e.g. MH-Agar) with Pseudomonas aeruginosa you can easily observe the diffusion of its pigments.

In my opinion, photosynthesis is a major reason for bacterial pigment production (chlorophylls, carotenoids) , e.g. green and purple sulfur bacteria. I nice review has been recently published: Stomp et al., ISME J 1:271, 2007. Besides photosynthesis, there are some other functions ranging from antibiotic activities (Nakamura et al., Biotechnol Bioproc Engin 8:37, 2003 ), UV protection (Tong and Lighthart, Photochem Photobiol 65:103, 1997), virulence (Liu and Nizet, Trends Microbiol 17:406, 2009), to anti-freezing agent.

Dear Daniel, microbial secondary metabolites include the production of antibiotics, pigments and even toxins, however, pigments depends on the types of bacteria that you have. For example, Violacein is produced by some probiotic bacteria like Jantinobacterium lividum (Gram-negative bacteria) which have been reported for confer anti-Bd properties in salamanders.

I think that you would read something about secondary metabolism in order to know more about that...

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2006.03155.x/pdf

Good luck!

There are many reason the bacteria to produce pigments.

1. Phototsynthesis

2. UV protection

3. Defense mechanisms

4.Secondary metabolites for storage of energy

5. Stress

It varies with environment differs in marine, terrestrial and space.

Good luck

agree wih C.M. Hernandez. It is mainly related to secondary metabolism. For instance Monascus purpureus which produces angkak (red pigment usually used in Chinese food products as natural colorant).

Bacteria produce colorful or colorless molecules for their own benefits. Bacteria make those molecules through incorporating various chemical units/groups that have different spectra properties, either colorful or colorless.

pigment molecules have the flexible abilities to be at several energetic levels changing the corresponding color, therefore the primary functions are the energy storage, transfer and filter. Other functions seem to be secondary in evolution from the ocean geochemical systems to the simplest ecosystems.

The suggestions and contributions from the experts are very informative and insightful of microbial biology, however i will add that bacteria pigments also aid in bacteria communication, or what i refer to as" Bacteria gossips and tiny conspiracies"

I agree with Helmut Brandl. Some pigments are produced for virulence for instance pyocyanin produced by Pseudomonas aeruginosa. Pyocyanin is toxic to prokaryotic and eukaryotic cells due to the reactive oxygen intermediates it generates, such as superoxide radical and hydrogen peroxide.

Here is a pigment that is produced by many strains of cyanobacteria, apparently as a protection against UV light: Scytonemin https://en.wikipedia.org/wiki/Scytonemin

I would just add that we believe that pigment is produced by certain bacteria e.g. Staph aureus as one of many virulence factors. George Liu and colleagues have published on this topic. We have measured the amount of pigment that are produced by different strains and the greater the pigment there seems to be a trend toward more antimicrobial resistance.

There are lot of compounds which has certain strong color, like the porphyrine based complexes as haemoglobin or chlorophyll. In many cases the color is not in obvious connection with the function. My last surprising experience was when the Paenibacillus macerans culture turned to be purple-brownish just after stopping airation.

I guess there are pretty many aspects of this diverse issue, and most of them is not 100% described - as it is not a surprise in microbiology.

@Istvan, thanks for your good note about change of color in Paenibacillus at O2 flux change. It indicates on the role of pigments as the molecular energetic stations transforming/filtering/accumulating different kinds of energy: radiation, chemical, thermic, etc. at a set of fixed E Potential levels, thus changing color at each jump from one level to another, up and down

Alexander, thanks for your remarks."pigments as the molecular energetic stations transforming/filtering/accumulating different kinds of energy: radiation, chemical, thermic, etc." this sentence works nearly as a definition, and seems to be wide enough to be correct. Maybe it would be good to add on more function: in many cases pigments are in the prostetic part of enzymes. Several times together with some special metal ion. (This is in complete accordance with your definition- all enzymes contributing in transforming chemical energy to a lower level of it with a different distribution pattern). Back to haemoglobin: probably the connection of poisonous CO with it gives a different E potential level: the resulting color is altered in carboxyhaemoglobin compared to the normal color. Anyhow, thanks, your comment was very helpful for me.

I have read the comments by different researchers... all are good and informative.

I would like to share my views

Bacterial/ microbial pigment is also due to response to some chemical that induces bacteria to secrete some secondary metabolites (they may be some pigment or antibiotic or organic compound). During my research, when I was culturing the isolate (sub-culturing), a simple change in chemical (inorganic salt) component in growth medium, my isolate produced red/pink pigment in the medium. I don't know what is that... as don't have the facility to analyse and funding.

So, I just want to say..pigment production/secretion by microbial isolate is not only primary metabolite, it may be secondary metabolite.

If anyone know how to check the type of pigment secreted by bacterial (Bacillus sp.) isolate, please guide me.

Thanks

To Kunal,

The red/pink pigment may be a Prodigiosin-like compound. Try acidic ethanol to extract it and check whether it has a maximal absorbance at about 535nm.

all these answers are very good and informative. I would like to add a little comment , some bacteria strains can produced pigment during their isolation and according to the environment of incubation. but some of them can also lose their pigment production when they were subculture several time like for example some strains of A. salmonicida

all the above comments are interesting and expand understanding for pigment functions. As for photosynthesis performed by phototrophic organisms, pigments play important role in light energy harvest , transfer and concersion of chemical energy. In addition to , they also performed photoprotection and stabiltity function for photosystem .

For non-phototrophic organisms, in my opinion, pigments perfomed mainly (photo-)protections,and are believed to act as a sunscreen units,especially for carotenoids

To Kunal,

you can scan directly the absorption spectrum of culture suspension range from from nm to 900nm,then observed the maximal peak so as to judge the pigment type. If the maximal absorption is located in the region from 400 nm- 600nm, may be it belongs to carotenoids. you can sent your results to me by email([email protected]), maybe, I can analyze it. my research interest focus mainly on photopigments. we have developed better the methods for qualitative and quantitative analysis of pigments.

From 300 nm to 900nm

mostly it is due to virulence, for example Pyocyanin a blue pigment that is a toxin produced and secreted by the Gram negative bacterium Pseudomonas aeruginosa. Pyocyanin is a secondary metabolite with the ability to oxidise and reduce other molecules and therefore can kill microbes competing against P. aeruginosa as well as mammalian cells of the lungs which P. aeruginosa has infected during cystic fibrosis.

other functions depend on the bacterial metabolism, whereby phototrophic bacteria have a photosynthetic metabolism, for example the purple sulfur bacteria which are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria.

Pigments can have a photoprotective function. They may also be providing some mode of communication. Pigments like prodigiosin and violacein have been shown to contain a variety of bioactivities (e.g. anticancer, antimicrobial, etc.). For photosynthetic bacteria, of course, pigments help in light capturing. But this area i.e. functional importance of pigment production certainly demands much more research.

Pigmentation is often 'inducible' by a variety of inducers; for e.g. light, temperature (cold), chemicals in growth medium. It helps bacterial against harmful radiation or some other kind of stress, which cells generally experience in their natural environment which is not present in the lab conditions which often results in loss of this characteristic in the lab condition.

very interesting observations / hypotheses! I feel we must experiment more on each hypothesis/observation.

could there be any phylogenetic component in pigment production!

does the color have relation to the function we have enumerated?

dear sir,

i think this will help you...i am giving u a reference...

http://www.biotecharticles.com/Applications-Article/Colorful-Bacteria-612.html

colour producing bacteria on leather substrate. 

Is there any relation between pigmented epi/endophytic bacteria and the application of chemicals to cultivated plants?

As far as I know the famous E. coli K12 has a long term special history.

Since culturing on solid media during decades, it has lost all possible pathogenic properties and moreover the ability to colonize the human gut. Therefore it is evaluated as gras (generally recognized as safe) and classified into the risk 1 group. I think the background is the lack of selection pressure, in such environment these properties were "expensive" to maintain and additionally these characteristisc were useless. Maybe you have the same situation (?)