ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel


Updated on February 11, 2015




These micro-organisms are special types of bacteria that contain light absorbing pigments called bacteriochlorophyll, and reaction centers which make them capable of converting light energy into chemical energy and allow them to photosynthesize.

All the photosynthetic bacteria are Gram negative bacteria. They are classified as follows:


These are also known as Green sulphur bacteria as they use reduced sulphur compounds as electron donor. Sulphur granules are located outside the cell. All of these carry out Anoxygenic photosynthesis. Their cells contain bacteriochlorophyll c or d located in chlorobium vesicles attached to the cytoplasmic membrane.

All the bacteria of this group are non-motile and occur in various shapes such as spheres, rods, and spirals. All bacteria can be able to survive in extreme conditions, like in the ocean near a black smoker in Mexico.


These are also known as Green nonsulphur bacteria as these cannot use reduced sulphur compounds as electron donor.they also carry out Anoxygenic photosynthesis. Unlike the chlorobi group, they are motile and motility is by using filaments. Members of this group can either be photoautotrophic (create their own energy through the sun’s energy); chemoorganotropic (requires a source of carbon); or photoheterotrophic (don’t use carbon dioxide for their carbon source).


This group is divided into two subgroups:

Purple sulphur bacteria (gama proteobacteria); e.g. Chromatium. As the name suggests these bacteria use sulphur and sulphide as the sole photosynthetic electron donor and sulphur can be oxidized to sulphate. They also use hydrogen sulfide as their reducing agent, which is why they give off sulfur rather than oxygen. They are also able to fix CO2 to live. They are short in size, about ~1 µm in diameter and 3-4 µm long.

Members of this group are found in either stagnant water or hot sulfuric springs, as they cannot photosynthesize in places that have an abundance of oxygen.

Purple sulphur bacteria can produce sulfur particles inside their cells, and hence, called as Chromatiaceae. It can produce sulphur particles outside their cells, and called as Ectothiorhodospiraceae.

Another subgroup of Proteobacteria is the Purple nonsulphur bacteria (alpha and beta proteobacteria; Rhodospirillaceae); e.g. Rhodospirillum. As the name suggests, these are not able to use elemental sulphur as electron donor and typically use an organic electron donor, such as succinate or malate; can also use hydrogen gas as its reducing agent. These can tolerate small amounts of sulfur, but are sensitive to too much hydrogen sulfide.

Members of this group can grow aerobically in the dark by respiration on an organic carbon source. All the cells helical in shape unlike the Purple sulphur bacteria, ~1 µm in diameter and variable in length. These contain bacteriochlorophyll a or b located on specialized membranes continuous with the cytoplasmic membrane.

The largest and most diverse group of photosynthetic bacteria is Cyanobacteria (Cyanophyta ): these are also known as Prokaryotic blue green algae as all are photoautotrophs. They are characterized by their ability to perform oxygenic photosynthesis using water as electron source.

All the members are widespread in soil, freshwater and marine habits. Some of the members are thermophilic forms. They use CO2 as their sole carbon source and light as their energy source. All store carbohydrates, lipids, and the nitrogenous cyanophycin. Among this group there is diversity in shape and arrangement from unicellular cocci or rods to long trichomes. The unicellular forms are non motile; trichome formers possess gliding motility. The G + C content of cyanobacteria is 35-71%.

Their Photosynthetic system closely resembles that of eukaryotes because they use the same photosynthetic pathway as eukaryotic cells such as algae and higher plants (the "C3" or "Calvin" cycle). They have chlorophyll a as major pigment; phycobiliproteins is present as an accessory pigment; and has photosystem II and oxygenic photosynthesis. The photosynthetic pigments and electron transport chain components are present in thylakoid membrane lined with phycobilisomes.

They show diversity in reproduction as binary fission, budding, multiple fission and fragmentation. Some forms contain small motile filaments called as Hormogonia. In unfavourable condition like desiccation, some forms develop dormant thick walled resting cells called Akinetes.

They can fix both nitrogen and produce oxygen. Use atmospheric nitrogen and convert it into nitrate and nitrite in some specialized cells called as Heterocyst, present in filamentous forms of cyanobacteria. Cyanobacteria forms symbiotic relationship with fungi in lichens. They have the distinction of being the oldest known fossils. Human relevance of the blue-green bacteria is that it occurs at the bottom of food chains, Produce blooms in water and cause undesirable effects in human water supplies.

Examples: Chemaesiphon: non motile; 31-71% G+C.

Pleurocapsa: only some are motile; 40-46% G+C

Spirulina, Oscillatoria, Lyngbya: motile: 34-67% G+C

Anabaena, Nostoc: motile, produce akinetes, 38-47% G+C

Geitleria: may produce akinetes; 42-44% G+C.

Importance of photosynthetic bacteria:

Photobacteria could have multiple biotechnological applications such as

Since all photosynthetic bacteria still possess ancient arrangement and structure of their photosynthetic apparatus. It also gives an evolutionary evidence for origin of chloroplasts.

The use of chemical reductants other than water by photosynthetic bacteria is a strong geological evidence to support the theory of ancient reducing atmosphere on the Earth.

The cyanobacteria have also been tremendously important in shaping the course of evolution and ecological change throughout earth's history.

Production of enzymes and pharmaceuticals for the simplest reason that no carbon source needs to be added in their growth medium. Researchers at Harvard’s Wyss Institute have engineered photosynthetic bacteria to produce simple sugars and lactic acid.

A Spirulina cyanobacterium is used as food. Some of them can also be used as animal feed

They have Potential application in bioremediation of polluted aquatic environments since they can grow and utilize toxic substances like H2S or H2S2O3.

The ongoing research is to use these bacteria to produce clean fuels using light energy in the process of photosynthesis.

Cyanobacteria are important providers of nitrogen fertilizer in the cultivation of paddy and beans.

Cyanobacteria are used as important Bio-fertilizers.





This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

Show Details
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
ClickscoThis is a data management platform studying reader behavior (Privacy Policy)