Aries
04-13-2012, 07:02 PM
Hey guys,
As some of you know I do a lot of microbiology I am obsessed with bacteria lol and I have recently written a paper which is going to be used as part of a larger study, for all of you science buffs and just people who are interested in that sort of thing I thought Id share it, personally I think it's fascinating where u can find bacteria they are everywhere! :-)
Despite the boom of discovering new actinomycete species within the past 50 years through bioprospecting, it was becoming relatively clear that fewer novel strains of actinomycetes are being discovered from known terrestrial soils. It was once thought that the biodiversity of these bacteria was very much cosmopolitan, meaning there was little diversity and they possessed constituent elements from around the world. All types of bacteria are found where their growth parameters are met. (Wawrik et al, 2007) Therefore the actinomycetes were traditionally considered as organisms which could not occupy natural ecological niches that were characterized by extreme conditions. Through the use of new biological screening systems this has been found to be untrue, as the yielding evidence indicates that microbial ecosystems especially those categorised as extreme harbour different and unique specimens. This problem for the time being however has been solved by using selective isolation procedures of novel actinomycetes from poorly understood habitats. (Goodfellow & Fiedler, 2010) As a result different varieties of actinomycetes can be considered extremophilic and extreme – tolerant bacteria as they can thrive in physically and geochemically stressing conditions in which other organisms would perish. The repertoire of environments in which these bacteria have been isolated includes hyper-arid soils, pH variable sediments, heavy metal contaminated soils and sediments acquired from hydrothermal vents. This but emphasises the tenacious nature of these bacteria.
Hyper arid and arid environments constitute a significant proportion of the world’s biomes usually taking the form of barren deserts. The Atacama Desert located in Peru within Chile is an example of a hyper arid environment. It is also known as the driest place on earth in which very little rainfall has ever been recorded. In extremely arid deserts such as the Atacama it is thought the high temperatures, ionizing radiation and low moisture content within the soils severely limits general microbial growth and the diversity of different species. But to the contrary, in the Atacama it is now thought the detectable microbial community is primarily composed of Actinobacteria, Proteobacteria and Firmicutes. (Lester et al, 2007) These bacteria have been found through the use of use phospholipid fatty acid signatures (PFLA) indicating a much larger diversity than once thought. Due to variable and hostile environmental factors in deserts such as fluxes of temperature, aridity and availability of water actinomycetes must exhibit unique attributes and properties which enable them to survive. Out of these communities the genus Streptomyces has been the most significantly isolated and in most cases actinomycetes were the only culturable bacteria to be isolated. (Okoro et al, 2009) Actinomycetes with, thermophilic, thermotolerant and psychrotolerant properties have been isolated which have arose because of variable temperatures in deserts. The desiccating temperatures through the day and relatively cold temperatures during the night has made it vital for these bacteria to adapt to these extreme conditions . Reasons for their survival in such extreme conditions can include the utilisation of a plethora of organic substances within the soils such as carbon and nitrogen. Streptomyces thermoautotrophicus is able to use carbon monoxide or a mixture of carbon dioxide and hydrogen in order to survive occupying a special place. (Zenova et al, 2011) By being able to utilise these different compounds, thermo tolerant and thermophilic actinomycetes could be considered as an integral part of maintaining soil fertility. They are able to utilise these compounds and processes such as the nitrogen cycle along with their well known degradation properties benefitting all organisms within this particular niche whilst also providing themselves with compounds essential for life. Another strategy which they employ is the production of thermo stable enzymes aiding their survival as they are able to withstand much higher temperatures; the pullanases have optimum temperatures of 80 - 95°C. (Eprintsev et al, 2005) It was also shown that in Saccharomonospora ximjinagenes specific thermostable phospholipids were found. These thermo stable products are heavily advantageous as these thermo stable enzymes do not undergo denaturation at lower temperatures and that these phospholipids are hardier than other bacterial species and are able to withstand the hardship placed upon them by the desert. The products which they produce aren’t only limited to enzymes but also commercial products such as antibiotics which can be used in clinical scenarios. Other strategies thermotolerant and thermophilic actinomycetes exhibit to cope with hyper arid conditions is manipulation of their growth cycles. Adapted growth cycles in temperatures between 20 – 50ºC with a maximal colony growth at 45ºC have been found along with their spores conferring a greater advantage over theses mycelial bacteria when compared to their unicellular counterparts.
Actinomycetes of a marine nature have come into the focus of taxonomists as it is evident that they are very widely distributed in marine environments and it is thought only 1% have been discovered. The most impressive and unique strains are those which are being discovered from deep sea sediments, in particular those from hydrothermal vents and deep sea trenches. Marine actinomycetes have attracted great attention since they have developed unique metabolic and physiological capabilities that ensure survival in extreme habitats. (Olano et al, 2009) The environmental conditions exhibited in the deep sea, especially within the vicinity of hydrothermal vents are some of the harshest conditions on earth. Due to fluctuating conditions of these hydrothermal vents, these bacteria and other organisms must deal with many different factors which would impede their functions. In some cases actinomycetes have been shown to form partnerships with other organisms such as sea slugs and other gastropod molluscs. There is also evidence to support vent symbionts produce metabolites that defend their host species. (Pettit, 2011) Therefore the stressing conditions which cause actinomycetes to produce secondary metabolites are able to benefit others in these diverse communities. Extreme variations in temperature are also witnessed from the colder surrounding water of the deep sea to the boiling plumes released from these deep sea vents therefore thermotolerant and psychrotolerant varieties prevail. The substances released from these plumes can also be toxic to bacterial life, as the release of acidic compounds and the mixing of alkaline substances presents another harsh aspect of this habitat. The most common types of actinomycete extremophiles which are found here are categorised as barophiles, organisms which have an affinity in pressurised conditions, thermophiles, acidophilic and acidotolerant organisms which are able to withstand and thrive in acidic conditions. Actinobacteria dominated strains obtained from untreated sediments; the lifestyle of these bacteria is adapted to minute nutrient concentrations (k-strategists). (Gartner et al, 2011) As a result this adaptation confers an advantage of other deep sea bacteria such as Gammaproteobacteria as survival and reproductive strategies accommodate low nutrient concentrations. Most notably a specific feature exhibited by terrestrial Streptomyces species in acidic conditions and substrates is their ability to alkalize acidic substances through intensification of their biochemical processes. (Zenova et al, 2011) In conjunction with this adaptation and manipulation of their growing mechanisms has also been shown to occur, such as the prolongation of their life cycle and inhibition of aerial mycelium formation and spore growth. The ability to be able to grow faster in order to change pH to a level more favourable for mycelia and spores therefore it is highly plausible these strategies are employed in alkaline conditions as and to a much greater degree in marine specimens as acidic and alkaline conditions are more intense. As a result from inhabiting these extreme conditions unique and structurally diverse polysaccharides, lipids, enzymes and natural products arise, many of which have extensive clinical applications.
The anthropogenic effects on nature can also effect the diversity of bacterial species habitats; as a result bacteria tolerant to wastes from industry have been observed namely in heavy metal contaminated soils. With the current growth of commercial industries such as mining, manufacturing and the waste from synthetic products such as pesticides and paints in free ionic forms heavy metals are particularly toxic as they are able to accumulate within the environment. At high enough concentrations excessive amounts of less toxic metals such as copper, iron and zinc can become toxic within humans, animal life and bacteria. However, heavy metals, like Hg, Cd, and Pb, of directly cause oxidative stress, lipid peroxidation, carcinogenesis, mutagenesis, and neurotoxicity on humans, animals, and plants at low concentrations. (Oyetibo et al, 2010) In studies regarding heavy metal resistance in bacteria considerable focus is placed on the actinomycetes especially Streptomycetes as in most cases they have exhibited the most potential in being resistant to heavy metals ranging from copper to cadmium. Actinomycetes indicate biodegradative activity as they are able to metabolise harmful recalcitrant molecules and break them down into their constituent elements making them less lethal. It has been witnessed that indigenous actinomycete strains isolated from heavily copper polluted soils have acquired physiological and genetic attributes which allow them to adapt to increased amounts of heavy metals. An actinomycete strain has shown the ability to remove more than 50% of copper from culture medium (39mg L-1). (Albarracin et al, 2005) Even actinomycetes which have not been isolated directly have been shown to resist conditions which would impede the growth of other bacteria. In a similar study regarding heavy metal resistance Streptomyces orientalis has been shown to produce a biosurfactant which has produced clear zones in media containing the heavy metal cadmium to great effect. Berkley Pit Lake an abandoned open – pit copper mine contaminated with high concentrations of dissolved metal sulphates has been the site of over 20 new metabolite discoveries. (Pettit, 2011) Within their natural environment bacteria of this nature must ensure their survival by producing a multitude of products therefore producing a product such as a biosurfactant which can neutralise a harmful substance such as a heavy metal will be advantageous and ensure the survival of that organism as the concentration of heavy metals in the soil will decrease. As a result considerable emphasis is placed on the applications of actinomycetes for human beneficence as they are heavily sought after in human industry for their use as bioremediative tools.
In conclusion there is conclusive evidence that the diversity of actinomycetes within different biological niches is very great and much larger than once conceptualised. From using new isolation procedures and DNA sampling techniques it is very evident that actinomycetes are some of the most if not the most extremophilic and adaptive discovered bacteria. What is also evident is that the number of these bacteria discovered is relatively small in number and that their extremophilic properties when exploited could lead to the discovery of new diverse natural products which could be of benefit in human use. Therefore it is extremely necessary that further studies should be carried out regarding these bacteria for future use.
As some of you know I do a lot of microbiology I am obsessed with bacteria lol and I have recently written a paper which is going to be used as part of a larger study, for all of you science buffs and just people who are interested in that sort of thing I thought Id share it, personally I think it's fascinating where u can find bacteria they are everywhere! :-)
Despite the boom of discovering new actinomycete species within the past 50 years through bioprospecting, it was becoming relatively clear that fewer novel strains of actinomycetes are being discovered from known terrestrial soils. It was once thought that the biodiversity of these bacteria was very much cosmopolitan, meaning there was little diversity and they possessed constituent elements from around the world. All types of bacteria are found where their growth parameters are met. (Wawrik et al, 2007) Therefore the actinomycetes were traditionally considered as organisms which could not occupy natural ecological niches that were characterized by extreme conditions. Through the use of new biological screening systems this has been found to be untrue, as the yielding evidence indicates that microbial ecosystems especially those categorised as extreme harbour different and unique specimens. This problem for the time being however has been solved by using selective isolation procedures of novel actinomycetes from poorly understood habitats. (Goodfellow & Fiedler, 2010) As a result different varieties of actinomycetes can be considered extremophilic and extreme – tolerant bacteria as they can thrive in physically and geochemically stressing conditions in which other organisms would perish. The repertoire of environments in which these bacteria have been isolated includes hyper-arid soils, pH variable sediments, heavy metal contaminated soils and sediments acquired from hydrothermal vents. This but emphasises the tenacious nature of these bacteria.
Hyper arid and arid environments constitute a significant proportion of the world’s biomes usually taking the form of barren deserts. The Atacama Desert located in Peru within Chile is an example of a hyper arid environment. It is also known as the driest place on earth in which very little rainfall has ever been recorded. In extremely arid deserts such as the Atacama it is thought the high temperatures, ionizing radiation and low moisture content within the soils severely limits general microbial growth and the diversity of different species. But to the contrary, in the Atacama it is now thought the detectable microbial community is primarily composed of Actinobacteria, Proteobacteria and Firmicutes. (Lester et al, 2007) These bacteria have been found through the use of use phospholipid fatty acid signatures (PFLA) indicating a much larger diversity than once thought. Due to variable and hostile environmental factors in deserts such as fluxes of temperature, aridity and availability of water actinomycetes must exhibit unique attributes and properties which enable them to survive. Out of these communities the genus Streptomyces has been the most significantly isolated and in most cases actinomycetes were the only culturable bacteria to be isolated. (Okoro et al, 2009) Actinomycetes with, thermophilic, thermotolerant and psychrotolerant properties have been isolated which have arose because of variable temperatures in deserts. The desiccating temperatures through the day and relatively cold temperatures during the night has made it vital for these bacteria to adapt to these extreme conditions . Reasons for their survival in such extreme conditions can include the utilisation of a plethora of organic substances within the soils such as carbon and nitrogen. Streptomyces thermoautotrophicus is able to use carbon monoxide or a mixture of carbon dioxide and hydrogen in order to survive occupying a special place. (Zenova et al, 2011) By being able to utilise these different compounds, thermo tolerant and thermophilic actinomycetes could be considered as an integral part of maintaining soil fertility. They are able to utilise these compounds and processes such as the nitrogen cycle along with their well known degradation properties benefitting all organisms within this particular niche whilst also providing themselves with compounds essential for life. Another strategy which they employ is the production of thermo stable enzymes aiding their survival as they are able to withstand much higher temperatures; the pullanases have optimum temperatures of 80 - 95°C. (Eprintsev et al, 2005) It was also shown that in Saccharomonospora ximjinagenes specific thermostable phospholipids were found. These thermo stable products are heavily advantageous as these thermo stable enzymes do not undergo denaturation at lower temperatures and that these phospholipids are hardier than other bacterial species and are able to withstand the hardship placed upon them by the desert. The products which they produce aren’t only limited to enzymes but also commercial products such as antibiotics which can be used in clinical scenarios. Other strategies thermotolerant and thermophilic actinomycetes exhibit to cope with hyper arid conditions is manipulation of their growth cycles. Adapted growth cycles in temperatures between 20 – 50ºC with a maximal colony growth at 45ºC have been found along with their spores conferring a greater advantage over theses mycelial bacteria when compared to their unicellular counterparts.
Actinomycetes of a marine nature have come into the focus of taxonomists as it is evident that they are very widely distributed in marine environments and it is thought only 1% have been discovered. The most impressive and unique strains are those which are being discovered from deep sea sediments, in particular those from hydrothermal vents and deep sea trenches. Marine actinomycetes have attracted great attention since they have developed unique metabolic and physiological capabilities that ensure survival in extreme habitats. (Olano et al, 2009) The environmental conditions exhibited in the deep sea, especially within the vicinity of hydrothermal vents are some of the harshest conditions on earth. Due to fluctuating conditions of these hydrothermal vents, these bacteria and other organisms must deal with many different factors which would impede their functions. In some cases actinomycetes have been shown to form partnerships with other organisms such as sea slugs and other gastropod molluscs. There is also evidence to support vent symbionts produce metabolites that defend their host species. (Pettit, 2011) Therefore the stressing conditions which cause actinomycetes to produce secondary metabolites are able to benefit others in these diverse communities. Extreme variations in temperature are also witnessed from the colder surrounding water of the deep sea to the boiling plumes released from these deep sea vents therefore thermotolerant and psychrotolerant varieties prevail. The substances released from these plumes can also be toxic to bacterial life, as the release of acidic compounds and the mixing of alkaline substances presents another harsh aspect of this habitat. The most common types of actinomycete extremophiles which are found here are categorised as barophiles, organisms which have an affinity in pressurised conditions, thermophiles, acidophilic and acidotolerant organisms which are able to withstand and thrive in acidic conditions. Actinobacteria dominated strains obtained from untreated sediments; the lifestyle of these bacteria is adapted to minute nutrient concentrations (k-strategists). (Gartner et al, 2011) As a result this adaptation confers an advantage of other deep sea bacteria such as Gammaproteobacteria as survival and reproductive strategies accommodate low nutrient concentrations. Most notably a specific feature exhibited by terrestrial Streptomyces species in acidic conditions and substrates is their ability to alkalize acidic substances through intensification of their biochemical processes. (Zenova et al, 2011) In conjunction with this adaptation and manipulation of their growing mechanisms has also been shown to occur, such as the prolongation of their life cycle and inhibition of aerial mycelium formation and spore growth. The ability to be able to grow faster in order to change pH to a level more favourable for mycelia and spores therefore it is highly plausible these strategies are employed in alkaline conditions as and to a much greater degree in marine specimens as acidic and alkaline conditions are more intense. As a result from inhabiting these extreme conditions unique and structurally diverse polysaccharides, lipids, enzymes and natural products arise, many of which have extensive clinical applications.
The anthropogenic effects on nature can also effect the diversity of bacterial species habitats; as a result bacteria tolerant to wastes from industry have been observed namely in heavy metal contaminated soils. With the current growth of commercial industries such as mining, manufacturing and the waste from synthetic products such as pesticides and paints in free ionic forms heavy metals are particularly toxic as they are able to accumulate within the environment. At high enough concentrations excessive amounts of less toxic metals such as copper, iron and zinc can become toxic within humans, animal life and bacteria. However, heavy metals, like Hg, Cd, and Pb, of directly cause oxidative stress, lipid peroxidation, carcinogenesis, mutagenesis, and neurotoxicity on humans, animals, and plants at low concentrations. (Oyetibo et al, 2010) In studies regarding heavy metal resistance in bacteria considerable focus is placed on the actinomycetes especially Streptomycetes as in most cases they have exhibited the most potential in being resistant to heavy metals ranging from copper to cadmium. Actinomycetes indicate biodegradative activity as they are able to metabolise harmful recalcitrant molecules and break them down into their constituent elements making them less lethal. It has been witnessed that indigenous actinomycete strains isolated from heavily copper polluted soils have acquired physiological and genetic attributes which allow them to adapt to increased amounts of heavy metals. An actinomycete strain has shown the ability to remove more than 50% of copper from culture medium (39mg L-1). (Albarracin et al, 2005) Even actinomycetes which have not been isolated directly have been shown to resist conditions which would impede the growth of other bacteria. In a similar study regarding heavy metal resistance Streptomyces orientalis has been shown to produce a biosurfactant which has produced clear zones in media containing the heavy metal cadmium to great effect. Berkley Pit Lake an abandoned open – pit copper mine contaminated with high concentrations of dissolved metal sulphates has been the site of over 20 new metabolite discoveries. (Pettit, 2011) Within their natural environment bacteria of this nature must ensure their survival by producing a multitude of products therefore producing a product such as a biosurfactant which can neutralise a harmful substance such as a heavy metal will be advantageous and ensure the survival of that organism as the concentration of heavy metals in the soil will decrease. As a result considerable emphasis is placed on the applications of actinomycetes for human beneficence as they are heavily sought after in human industry for their use as bioremediative tools.
In conclusion there is conclusive evidence that the diversity of actinomycetes within different biological niches is very great and much larger than once conceptualised. From using new isolation procedures and DNA sampling techniques it is very evident that actinomycetes are some of the most if not the most extremophilic and adaptive discovered bacteria. What is also evident is that the number of these bacteria discovered is relatively small in number and that their extremophilic properties when exploited could lead to the discovery of new diverse natural products which could be of benefit in human use. Therefore it is extremely necessary that further studies should be carried out regarding these bacteria for future use.
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