HABITATS (1)

BY: K. Sai Manogna (MSIWM014)

For a human being who is 890,000 times larger than an E.coli cell, it is difficult to think of microbial environments on the order of micrometres to thousands of meters. Conditions like oxygen or pH will drastically change over this time. It creates microenterprises, and ecosystems are therefore more patchy than stable. Different abiotic factors influence and help establish these microenvironments in microbial communities in these habitats. Any disruption can lead over time to changes in microbial populations in habitats.

Table: Effects of abiotic factors:

Abiotic factors	Range of States
O2 Level	Anoxic-microoxic-oxic
Salinity	Hypersaline-marine-freshwater
Moisture level	Arid-moist-wet
pH	Acidic-neutral-alkaline
Temperature	Hot-warm-cold
Light level	Aphotic-low level-bright-UV

The Niche:

The ‘niche’ turning to the general ecological literature shows that there is what is known as the ‘fundamental niche,’ which reflects all environmental factors. In the ecosystems, the environment affects a species’ ability to survive and reproduce in the environment. The ‘realized niche’ is also the proper niche when biotic interactions (i.e., competition) restrict a species’ growth and reproduction. The definition of niche has been extended to microscopic organisms, enabling bacteria and archaea to exploit new niches not available to parentage by acquiring new genes through horizontal transmission. This niche definition for bacteria and archaea focuses more on the organism’s acquisition of new functional ability by transmitting horizontal genes, which implies a more complex character for niche boundaries. The survival and best reproduction niche of Ferroplasma are characterized by acidic, stable, rich in iron and heavy metals, and moderate temperatures. These conditions distinguish Ferroplasma’s niche space. Species also may change their climate so that other species have a more or less habitable environment.

Aquatic Habitats:

The oceans and flowing water bodies, for example, rivers and streams, range in aquatic ecosystems. Water, more than 97% found in the world’s oceans, covers nearly 71 percent of the earth’s surface. In streams, rivers, and lakes, less than 1 percent of water is contained. Water is continuously renewed through the hydrological cycle in all those various marine ecosystems. The scale of aquatic environments and their diversity suggests the significance for microorganisms of aquatic habitats. Key microbial players in aquatic environments include primary production phototrophs and the heterotrophs involved in carbon cycling in aquatic habitats.

In these marine settings, the environmental and physicochemical conditions vary greatly. Water movement is one of the apparent factors; streams and rivers will flow quickly, with lakes moving less. Winds produce surface water movement in the seas, create ocean waves, and create upwelling areas. These winds transfer nutrients, organisms, oxygen, and heat worldwide, in addition to deep-water currents. As in the seas, water circulation in all marine environments determines different properties of water. Physicochemical factors, such as the pH, the abundance and availability of macro-and micronutrients, salinity, phosphorus, nitrogen, sulphur, and carbon, can vary significantly within the various ecosystems.

Table: Characteristics of different aquatic habitats:

Aquatic habitat	Temperature range	Salinity (%)
Oceans	-1.5 to 27oC at surface	3.5
Rivers	0-30oC	0.001-0.05
Lakes a. freshwater b. great salt lake	4-50oC	0.01 avg. 12%

Storms are very fluid, have significant variations in physical and chemical environments, are greatly affected by their drainage range, and have a single water flow. In contrast, the lakes, particularly the stream’s headwaters, have more stable conditions and primary productivity. Lakes can be acidic or alkaline (e.g., Mono Lake, California), but often they can be saltier than freshwater, like the Great Salt Lake, Utah.

Aquatic microbial ecology has been advanced from descriptive research on who’s home” to hypothesis-driven studies of interactions and environmental and biological controls on the diversity and population distributions. A broad range of anti-predating mechanisms, including the secretion of exopolymer substances and capsules made up of polysaccharides and morphologic adaptations, are two of the exciting features and the subject of several studies. They are gram-positive. Studies have focused on how predators evade microbial communities, like predation, particularly by protists, and virus lysis is a significant mortality factor. Viruses in various aquatic environments are standard, with a difference of between one or two orders in size in these different habitats, while in freshwater, the abundance of the virus is more seasonal. In aquatic settings, what governs viral abundance is still under review.  In aquatic environments, viruses have a vital role in recovering organic matter dissolved by lysing their presence into their bodies, converting the carbon and other nutrients.

a. Fresh Water

The word wetlands for freshwater generally applies to rivers, streams, reservoirs, lakes, and groundwater. Freshwater that contains less than 1.000 mg/ l dissolved solids is classified under the United States Geological Survey (USGS). As noted above, freshwater microorganisms vary greatly from marine environments in their phylogenetic diversity. Typical freshwater bacterial classes include beta-proteobacteria (e.g., the relative of Rhodoferax and Polynucleobacter necessarius), Actinobacteria, Cytophaga/Flexibacter/Flavobacterium hydrolysis relatives.

b. Lakes:

Lakes are aquatic lakes, initially formed by glaciation, volcanism, or tectonics. The Great Lakes in North America, and Lake Baikal, Siberia, comprise approximately 40% of the world’s freshwater at a few vast lakes.

There are many gradients within water bodies that affect microbial distribution populations. The oxygen gradient is one of the most critical. In lakes where upper waters can be oxic and warmer, the lower gradient is colder and often anoxic. The thermocline is separated by these two layers, which is a transition region between the two layers. Seasonal changes in atmospheric temperature and water temperature can result in changes in density that turn the water over and allow oxygenated water to enter the lake’s lower reaches. It influences the microbial communities of the lake.

The vegetation around lakes supplies some nutrients that have been found in lakes. Low nutrient quantity lakes are oligotrophic, while high nutrient quantities, productivity, and oxygen depletion can affect species that can survive under such conditions. Lakes are eutrophic. The transformation of contaminants such as sulphur dioxide and nitrous oxide (NO₃) into acid rain causes some lakes to be naturally acidic while other acidic. Lakes in North-East America recover from acid rain impacts. The pH of the water in lake also influences the population of microbes.

c. Rivers and Streams:

During and after a rainstorm, the water will change and get a water movement force in rivières. Water is moving in streams and rivers through vast material, soil, trees, rocks, and other substances. It ensures a steady supply of nutrients to biotic communities and a great deal of trouble during floods. Many rivers cross cities and thus are exposed to human wastewater and other contaminants that can directly affect the river’s population. As the metabolic diversity of microorganisms is such that specific contaminants are potential energy sources in microorganisms. Since high organic loading can result in high productivity that diminishes oxygen levels, areas of urban rivers can be anoxic, limiting microorganisms in such regions.

The ecosystem of the river consists of many components like horizontal

(1) the active channel that can go dry part of the year in some rivers and streams and

(2) the transitional zone between the marine and the terrestrial habitats, in the riparian zone.

Vertically, streams and rivers are marked by

(1) Waters of the surface;

(2) the sub-surface water region of the hyporheic zone;

(3) the phreatic groundwater field.

The physicochemical properties of these ecosystems differ. Rivers and streams have many suspended organic and inorganic particles, restricting how much light penetrates the water column. At least partly shaded by trees that hang over the streams, the parts of the reaches have extensive vegetation. The extent of photosynthesis in the streams is restricted by both turbidity and shading. Desert streams are much higher than in tropical and temperate regions and have no shading of microbial photosynthesis. Rivers and rivers differ in their salinity by order of magnitude; desert rivers have the highest amounts.

d. Hot Springs:

Springs are springs of geothermal water, groundwater which comes into contact with hot rocks or magma from the world’s earth’s crust in volcanically active regions. Some impressive examples are found in Yellowstone’s national park in Wyoming, Iceland, Japan, and New Zealand.  Hot springs reflect extreme temperature conditions and, in some cases, pH. There is a high concentration of anaerobic or microaerophilic hot spring that suggests low oxygen concentrations. In hot springs where temperature limits are photosynthesis, they were suggested to be primordial producers. Hyperthermophiles, who use carbon dioxide as their carbon source, are also chemoautotrophs and serve as primary producers within hot spring ecosystems. Hot springs contain various gases, including molecular hydrogen and a reduced number of iron and sulphur compounds, dissolved and provide electron donors. It implies that Yellowstone’s primary productivity results from molecular hydrogen oxidation, which can happen to levels above 300 nM. in hot springs. Hot springs are the prime habitat for archaeological animals.

Marine habitats:

a. Oceans: 

In addition to the fact that it is a saline ocean rather than a terrestrial habitat. It is one of several environmental parameters that influence the existence of marine habitat microorganisms. Furthermore, temperature, light, food supply, and pressure vary from the surface to the ocean’s depths. The ecosystems of the ocean shift from shore to vertical depth. Traveling further into the water, from the surface or epipelagic region to the mesopelagic zone (200–1000m), you move into the bathypelagic zone (1000–4000m), the abyss area (4000–6000m), and eventually the Hadean area (<6000m).

b. Food and Microbial Aquatic Habitats:

The marine food web is typically characterized by the low nutrient abundance and patchy nature of the gradients, as mentioned above, and high salinity.

Although the food web has been studied on the ocean for more than a hundred years, several recent findings have led us to believe that the classical description of a chain from diatoms through copepods and to fish and whales can only be a small part of the energy flow. Recent studies of microorganisms, organic dissolved matter, and organic particles in the sea have shown other mechanisms by which a significant share of the energy available will flow. For decades, marine scientists have been cautiously approaching this food web view, and care should be taken when a paradigm is challenged.