Microbial Ecology: Their Relationship with One Another and the EnvironmentAmber WilliamsNortheastern State University
Might try breaking up into more paragraphs and have headings. Good paper


Microbial Ecology is the study of microbes in the environment and their interactions with each other. Microbes are the tiniest creatures on Earth, yet despite their small size, they have a huge impact on us and on our environment. Microbial ecology can help answer some of our most practical questions such as "How can we improve our lives?" as well as basic questions such as "Why are we here?" The study of microbial ecology can help us improve our lives via the use of microbes in environmental restoration, food production, bioengineering of useful products such as antibiotics, food supplements, and chemicals. The study of these bizarre and diverse creatures that are everywhere yet nowhere to be seen is fascinating and a pursuit that appeals to the curiousity and playfulness in us. Most types of microbes remain unknown. It is estimated that we know fewer than 1% of the microbial species on Earth. Yet microbes surround us everywhere -- air, water, soil. An average gram of soil contains one billion (1,000,000,000) microbes representing probably several thousand species. Microbial ecology is the study microbes in their environment. Microbes are found in water, in soil and in the atmosphere.
Microbial ecology is the study of the role of microbes which appear to be necessary for the functioning of life on Earth. Microbial ecologists seek to understand how microbes affect the environment on a global scale. Microbes probably contribute to global change, nutrient cycling, and ozone depletion. Microbial ecology is the study of microbial interactions with plants and with animals and with other microbes. Microbial ecology is an applied science. Knowledge of microbial ecology contributes to environmental protection, agriculture, mining, food production, and chemical and pharmaceuticals production. Microbial ecology is a rapidly developing scientific discipline. The reasons for this include the realization that microbes are essential for a healthy environment; they are important in helping us understand the mechanics of evolution; and they are important in biotechnology.
The Department/Section of Microbial Ecology was established in 1972 as an independent research unit specializing in ecological aspects of microbial life and the unit was in this year physically moved from the Department of Microbiology to a newly established Department of Ecology (at that time in the Ecology Building at Helgonavägen 5) at Lund University. Microbial ecology research in Lund was initiated by Docent Börje Norén (1919-1983) who in 1960 became the leader of a group of students and researches. The group was first located within the Department of Plant Physiology (headed by Prof. Hans Burström) and in 1967 it moved to and merged with the new Department of Microbiology (headed by Prof. Claes Weibull).During the years 1972-75 the group, now containing about 10 people, was studying soil microorganisms and microbial control mechanisms in soil. This direction of research was still continued after Börje Norén departure in 1975 for the Swedish Agricultural University (SLU) in Uppsala where he became professor at their Department of Microbiology. In 1975 Docent Birgit Hertz (from 1987 as a Professor) became the head of the group and continued as such until her retirement in 1989. Two main research directions developed during this period: general soil microbiology (with an emphasis on fungi) and ecology of nematophagous fungi. Both directions received international recognition, and were financed by research grants that mainly came from the Swedish Natural Science Research Council (NFR) and the Agricultural Research Council (SJFR).
These two research directions were complementary, and they were further linked in the late 70's when a national project on interactions in the rhizosphere was initiated. As a logical consequence studies on mycorrhiza symbiosis started in the early 80's which have gradually developed into its strong present position.In the 1980's the research group became more independently established. An undergraduate course in Microbial Ecology was offered for the first time in 1979. A few years later (1982) Bengt Söderström received a position as Docent at the Lund University (the first university financed position in microbial ecology) and the group, now about 20 people became a separate division within the Department of Ecology (founded in 1985). Further funding was obtained from the university, and in 1987 a chaired professorship in Ecological Microbiology was allocated at the Section of Microbial Ecology and the first holder was Bengt Söderström (appointed in 1990).The Department of Ecology in 1994 moved into a new building at Sölvegatan 37. Then the section of microbial ecology has continued a very successful research activity in the areas of microbial interactions with higher organisms (nematophagous fungi and mycorrhiza) as well as microbial activity in soils. In 2009 the staff consist of 3 professors, 1 lecturer, 2 assistant professors, a variable number of postdocs and about 10 PhD students.
An environmental source of cholera was hypothesized as early as the late nineteenth century by Robert Koch, but not proven because of the ability of Vibrio cholera, the causative agent of cholera, to enter a dormant phase between epidemics. Standard bacteriological procedures for isolation of the vibrios from the environmental samples, including water, between epidemics generally were unsuccessful. Vibrio cholera, a marine vibrio requiring salt for growth, enters into a dormant 'viable but non-culturable' stage when conditions are unfavourable for growth and reproduction. The association of V. cholera with plankton, notably copepods, provides evidence for the environmental origin of cholera, as well as an explanation for the sporadic and erratic nature of cholera epidemics. Thus, the association of V. cholera with plankton was established only recently, allowing analysis of epidemic patterns of cholera, especially in those countries where cholera is endemic. The sporadic and erratic nature of cholera epidemics can now be related to climate and climate events, such as El Niño. Since zooplankton have been shown to harbour the bacterium and zooplankton blooms follow phytoplankton blooms, remote sensing can be employed to determine the relationship of cases of cholera with chlorophyll, as well as sea surface temperature (SST), ocean height, and turbidity.
Cholera occurs seasonally in Bangladesh with two annual peaks in the number of cases occurring each year. From the data obtained and analysed to date, when the height of the ocean is high and sea surface temperature is also elevated, cholera cases are numerous. When the height is low and sea surface temperature is also low, little or no cholera is recorded. From the examination of data for the 1992-1993 cholera epidemic in India, preliminary comparisons of cholera data for Calcutta show a similar relationship between cholera cases, ocean height and SST. In conclusion, from results of studies of SST, phytoplankton and zooplankton, and their relationships to incidence of cholera, correlation of selected climatological factors and incidence of V. cholera appears to be significant, bringing the potential of predicting conditions conducive to cholera outbreaks closer to reality. Microbes play numerous key roles in global change, often as silent partners in human activities such as agriculture, mining and waste treatment. Complex interactions among humans, microbes and the rest of the biosphere have created some of our most challenging global problems. Recent discoveries reveal that human activities can dramatically affect the role of microbes in Earth’s climate.Human-induced warming and other environmental changes alter greenhouse gas production by microbes and intensify ongoing global shifts in climate. For instance, elevated temperatures may increase both methane and CO2 emissions from the vast northern peatlands, leading to further increases in warming. Interactions such as these among humans, microbes and climate need careful consideration since they can significantly worsen climate change and seriously hinder ongoing and planned efforts to minimize climate-related problems.
Relationships among atmospheric composition, climate change and human, animal and plant health merit serious study. Outbreaks of a number of diseases, including Lyme disease, hantavirus infections, dengue fever, bubonic plague, and cholera, have been linked to climate change. Fluctuations in disease incidence can be related to climate-dependent changes in the numbers of pathogen vectors such as mosquitoes, ticks and rodents. Changes in mosquito populations are especially concerning since mosquito-borne microbial diseases kill a large fraction of the human population. Climate change can also directly affect the distribution and abundance of pathogens themselves, thus increasing the prevalence of disease in humans, animals and plants. Microbes respond to a variety of other disturbances within the biosphere. Although the exact mechanisms are sometimes unclear the consequences can be positive or negative.We know that microbes in general mediate numerous biogeochemical reactions, and in aquatic systems form the base of food chains that sustain organisms from fish to humans. Terrestrial and aquatic microbes also significantly influence global conditions,which is hardly surprising since microbes outnumber by far all other organisms in rivers, lakes, oceans, and on the land. Some of these microbes react to human disturbances by mobilizing toxic elements such as mercury, selenium and arsenic, producing unexpected serious environmental problems. For example, microbes convert dissolved mercury into a highly toxic, volatile form that disperses through the atmosphere with global consequences. Other microbes can detoxify a variety of hazardous pollutants and elements introduced into the environment by human activity.However, the net balance of human-caused disturbances on aquatic and terrestrial microbes and their many activities, deleterious and beneficial, is unknown. Nonetheless, it is clear that the microbial world responds to human activity with results that often are surprising and highly undesirable.
Massive algal blooms resulting from excess nitrogen and phosphorous carried into rivers, lakes and oceans are one of the consequences of human activity. Large blooms, such as those in the Gulf of Mexico, lead to aquatic oxygen depletion, substantially degrading marine ecosystems and limiting their use as sources of food, water and recreation. Some evidence suggests that "red tides," "brown tides" and other harmful algal blooms are increasing in frequency and severity. Blooms of a marine dinoflagellate, Pfiesteria piscidica, which have been linked to coastal pollution, were essentially unknown 20 years ago, but now produce large fish kills on the southeast coast of the United States.Yet it is conceivable that algal blooms might be managed to reduce the impact of human-related CO2 emissions. The intentional addition of iron nutrients in some areas of the ocean might stimulate algae to convert more atmospheric CO2 into biomass. Ultimately this could lower CO2 concentrations and reduce the greenhouse effect. Similar management of microbes and plants in terrestrial systems might also help to mitigate CO2 accumulation. However, the complexities of numerous direct and subtle linkages among nutrient pollution,algal blooms, aquatic bacteria, disease, trace gases such as methane and nitrous oxide, climate,and human disturbances are only now beginning to be understood. Much more work is necessary before algal, plant and microbe management can be considered as a tool for climate control.

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All Tropical Forests organisms are dependent to some extent on bacteria and fungi. Some animals such as wood and leaf-eating insects depend on symbiotic gut microbes to digest cellulose in their food supply, while other insects utilize fungi directly as a food source. Without microbes, organic matter on the forest floor and in the soil would never decompose. The rate at which these microorganisms decompose dead material is directly responsible for the availability of nutrients for plants. As the humidity and temperatures in rainforests are high, conditions are ideal for rapid microbial decomposition. However, the rates of decomposition will differ according to which microorganisms are present, the character of the organic matter, the physical and chemical environment of the soil and so forth. Apparently microbial and fungal populations are quite sensitive to fluctuations in soil moisture and other disturbances. Nitrogen fixation is an essential function of microbes in forests. Without bacteria which are capable of converting gaseous nitrogen into nitrates and nitrites which plants can utilize, rainforest soils would rapidly become depleted of this essential mineral in usable form. Many million tons of nitrogen are converted annually and added to the soil by these organisms. In the many tropical soils which are nutrient-poor, only nitrogen-fixing bacteria allow plants to survive. Pathogenic microbes play a role in preventing "clumping" of trees or plants of a particular species and ensuring their wide dispersal throughout the forest.
When plants of one species live close together, they are subject to attacks by pathogenic agents, while if they are more widely dispersed, transmission of disease agents is more difficult. In this way, the presence of microbial and fungal pathogens play a role in structuring the composition of tropical forests, by ensuring that most individuals of a given (tree) species will be fairly widely dispersed (van der Putten, 2000). This has implications for monocrops, such as oil palm, soy beans, and rubber, which are being raised on converted rainforest land in many tropical areas. For example, the large gaps in the forests made to create oil palm forests in Malaysia and Indonesia have contributed to the spread of the root-rot fungus Ganoderma, and another root-rot fungus, Phytophthora cinnamon, spread widely after logging in Australia. Similarly, cutting in Eucalyptus forests in Australia has led to a great increase in severity of outbreaks of this pathogen. These outbreaks have many ancillary effects, including alterations in forest structure, changes in animal populations (including endangerment of rare species), and decreases in tree density. Microbes provide food for many small organisms in forests and also as agents which allow the digestion of otherwise indigestible food sources in the guts of many animals.
Fungi are important food sources for some invertebrates such, as ants and their fungus gardens and beetles. On the island of Sulawesi, 40% of the beetles feed on fungi. Many fungi are present in rainforest soils, and some form close associations with tree roots. These presumably symbiotic associations are known as mycorrhizae. Certainly the associations, in which the fungal hyphae penetrate or ensheathe the root, are very close, although they may not all be beneficial to the plant. Up to 90% of all tree roots are involved in these associations. The fungi colonize roots through the spread of the hyphae or the dispersion of spores. The exact role of mycorrhizae in forest ecology is not clear. Some believe that they are involved in nutrient capture and that much carbon and other minerals (nitrogen and phosphorus, especially) are transferred from the soil to the roots by mycorrhizal associations. In turn, the plant passes manufactured carbon compounds to the fungi, and since the mycorrhizae are themselves eaten by soil organisms, carbon is transferred rapidly from the host tree to the soil ecosystem. Mycorrhizae apparently facilitate the uptake of water by roots and increase the resistance of roots to pathogens.
All in all, mycorrhizal associations appear to play key roles in growth, nutrient cycling and primary productivity in tropical rainforests. They also appear to have some control over the structure of the plant community and the course of succession. Where forest is disturbed, plants which do not form mycorrhizal associations will predominate; later, as the fungi invade the area, there will be a succession of plants which tolerate and, later, require these associations. This scenario is complicated by the fact that fungi also undergo succession, and that these changes may play a role in the successional dynamics of plant species.Mycorrhizal fungi also act as social agents, as they interconnect trees through their hyphae. This may mean that trees can transfer carbon among themselves via the fungal mat, so that trees in the shade (and thus less able to photosynthesize) are "subsidized" by well-illuminated trees. It is possible that young trees in shady environments are enabled to survive by this mechanism, at least until they can extend their branches into the canopy. It has been speculated that forests are less competitive than they appear, particularly if the mycorrhizae act to reduce competition for nutrients by equitable distribution. In one experiment, tree seedlings were found to transfer carbon between species bidirectionally.
However, little is known about the role of mycorrhizae in tropical forests, and therefore one must be cautious about assessing the roles of these fungi in these ecosystems.Little is known about the ecology of mycorrhizae, but they appear to have a narrow range of tolerance; some can colonize more than one species of tree; others apparently cannot. Mycorrhizae don’t seem to reform easily in disturbed or logged environments. In one experiment, seedling roots became infected with fungus only when they were in contact with living mycorrhizal-root associations during the early stages of their growth. We don’t even know if all of these associations are essential or beneficial to the tree. However, if these associations are important, as they appear to be, disturbances of forests by logging may contribute to further forest destruction by disrupting them.
Endophytes are microbes that colonite living, internal tissues of plants without causing any immediate overt megative effects. Of the myriad of ecosystems on earth, those having the greatest biodiveristiy seem to be the ones also having endophytes with the greatest number and the most biodiverse microorganisms. Tropical and temperate rainforests are the most biologically diverse terrestrial ecosystems on earth. The most threatened of these spots cover only 1.44% of the land’s surface, yet, they harbor over 60% of the world’s terrestrial biodiversity. As such, one would expect that areas having high plant endemism also possess specific endophytes that may have evolved with the endemic plant species.


Ultimately, biological diversity implies chemical diversity because of the constant chemical innovation that exists in ecosystems where the evolutionary race to survive is the most active. Tropical rain forests are a remarkable example of this type of environment. Competition is great, resources are limited and selection pressure is at its peak. This gives rise to a high probability that rain forests are a source of novel molecular structures and biologically active compounds. It also describes a metabolic distinction between tropical and temperate endophytes through statistical data which compares the number of bioactive natural products isolated from endophytes of tropical regions to the number of those isolated from endophytes of temperate origin. Not only did they find that tropical endophytes provide more active natural products than temperate endophytes, but they also noted that a significantly higher number of tropical endophytes produced a larger number of active secondary metabolites than did fungi from other tropical substrata. This observation suggests the importance of the host plant in influencing the general metabolism of endophytic microbes.


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Microbial Ecology of Tropical Soils. New York: Nova Science, 2011. Print