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The bacteria then overwinters within the plant tissues, insect hosts, or in the soil and lay dormant until the conditions are right again to reproduce. If the infected storage organs are being used to propagate the plant, or if infected seed was produced, then when spring comes the bacteria will begin to grow just as its host does.
Plants can form new chemicals that can break down minerals, both directly [101] and indirectly through mycorrhizal fungi [25] and rhizosphere bacteria, [102] and improve the soil structure. [103] The type and amount of vegetation depend on climate, topography, soil characteristics and biological factors, mediated or not by human activities.
Some nitrogen-fixing bacteria have symbiotic relationships with plants, especially legumes, mosses and aquatic ferns such as Azolla. [4] Looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. Nitrogen fixation occurs between some termites and fungi. [5]
The pH level of concrete greatly influences what microbes can reproduce and how much damage is done to the concrete. A concrete surface is alkaline, making it difficult for microbes to germinate. However, chemical processes by the environment and microorganisms themselves cause changes in the concrete.
According to a 1996 study by H. L. Erlich in Chemical Geology journal, the self-healing ability of concrete has been improved by the incorporation of bacteria, which can induce calcium carbonate precipitation through their metabolic activity. [111] These precipitates can build up and form an effective seal against crack related water ingress.
The bacteria also infect the roots, leading to the formation of nodules. Actinorhizal nodules consist of several lobes, each lobe has a similar structure as a lateral root. Frankia is able to colonize in the cortical tissue of nodules, where it fixes nitrogen. [8] Actinorhizal plants and Frankias also produce haemoglobins. [9]
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Limestone generated inside the matrix of concrete may result in the densification of the matrix by pore filling and can help to self-heal crack, reducing its (water) permeability and resulting in the recovery of lost strength. If circumstances are favorable, most bacteria can precipitate CaCO 3 from the solution. [30]