Just as in the Eukarya and the Bacteria, members of the Archaea need to export proteins beyond the cell membrane. This would be required to fulfill a variety of essential functions such as nutrient acquisition and biotransformations, maintenance of extracellular structures and more. Apart from the Eukarya and the Bacteria however, members of the Archaea share a number of unique characteristics. Does this uniqueness extend to the protein secretion system? It was the objective of this study to answer this question. To overcome the limited experimental information on secreted proteins in Archaea, this study was carried out by subjecting the available archaeal genomes, which represent halophiles, thermophiles, and extreme thermophiles, to bioinformatics analysis. Specifically, to examine the properties of the secretomes of the Archaea using the ExProt program. A total of 24 genomes were analyzed. Secretomes were found to fall in the range of 6% of total ORFs (Methanopyrus kandleri) to 19% (Halobacterium sp. NRC-1). Methanosarcina acetivorans has the highest fraction of lipoproteins (at 89) and the lowest (at 1) were members of the Thermoplasma, Pyrobaculum aerophilum, and Nanoarchaeum equitans. Based on the Tat consensus sequence, contribution of these secreted proteins to the secretomes were negligible, making up 8 proteins out of a total of 7105 predicted exported proteins. Amino acid composition, an attribute of signal peptides not used as a selection criteria by ExProt, of predicted archaeal signal peptides show that in the haloarchaea secretomes, the frequency of the amino acid Lys is much lower than that seen in bacterial signal peptides, but is compensated for by a higher frequency of Arg. It also showed that higher frequencies for Thr, Val, and Gly contribute to the hydrophobic character in haloarchaeal signal peptides, unlike bacterial signal peptides in which the hydrophobic character is dominated by Leu and Ile.
Northern Ontario (Canada) especially the Greater Sudbury region is highly known for its nickel, copper and other metal deposits. The mining, roasting and smelting of these elements have caused disastrous effects on the vegetation and overall environment. Dolomitic lime which contains calcium and magnesium carbonate was applied to soils from 1980 to 1995 at different locations across Northern Ontario. The objective of the present study is to determine fungi diversity and abundance in selected limed and unlimed areas contaminated with metals in the Region. Soil respiration, fungi cultures and Phospholipid Fatty Acid (PLFA) were analyzed. The liming did maintain an increase in soil pH from extremely acid to slightly acid, even 25 to 30 years after liming applications. A total of 52 fungi species belonging to 34 genera were identified on growth media. The majority of fungi (up to 70%) in all the sites belong to the Ascomycota phylum. Some species were specific to one or two sites, while others were present in the majority of the sites. Fungal diversity and abundance were higher in limed soils compared to unlimed samples based on SDA medium growth. The rates of soil respiration in limed sites were also higher compared to unlimed areas. Phospholipid Fatty Acid (PLFA) analysis revealed a significantly higher total microbial biomass in samples from limed areas compared to unlimed samples. Total and arbuscular mycorrhizal fungi abundance based on this analysis followed the same trend. Surprisingly, there were 7 to 10 fold more bacteria than fungi in all the sites. Moreover, there was twice more Gram (-) bacteria than Gram (+) indicating that the sites are still severely stressed. Soil pH appears to be the most important factor for microbial abundance, diversity and activities than total metal content.
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