Summary: Land‐use change has been identified as the most severe threat to biodiversity. Soils are important biodiversity reservoirs, but to what extent conversion of high‐altitude temperate forest to arable land affects taxonomic and functional soil biodiversity is still largely unknown. Shotgun metagenomics was used to determine the taxonomic and functional diversity of bacteria, archaea and DNA virus in terms of effective number of species in high‐altitude temperate oak and pine‐oak forest and arable soils from Mexico. Generally, the soil ecosystem maintained its microbial species richness notwithstanding land‐use change. Archaea diversity was not affected by land‐use change, but the bacterial diversity decreased with 45–55% when the oak forest was converted to arable land and 65–75% when the pine‐oak forest was. Loss in bacterial diversity as a result of land‐use change was positively correlated ( R ² = 0.41) with the 10–25% loss in functional diversity. The archaeal communities were evener than the bacterial ones, which might explain their different response to land‐use change. We expected a decrease in DNA viral communities as the bacterial diversity decreased, i.e. their potential hosts. However, a higher viral diversity was found in the arable than in the forest soils. It was found that converting high altitude oak and pine‐oak forests to arable land more than halved the bacterial diversity, but did not affect the archaeal and even increased the viral diversity.

The genome sequence of Pantoea agglomerans UADEC20 is presented, which is a strain isolated from agricultural fields in northeast Mexico. The genome was assembled into 13 scaffolds, constituting a total chromosome size of 4.2 Mbp, with two of the scaffolds representing closed plasmids. The strain exhibits activity in phosphate solubilization and exopolysaccharide (EPS) production and secretion; therefore, we explored its biotechnological potential via its genome sequencing and annotation. Genomic analyses showed that a total of 57 and 58 coding sequences (CDSs) related to phosphate solubilization and EPS production were identified within its genome, in addition to a reduced number of CDSs related to drug resistance and phages. The comprehensive set of genes supporting phosphate solubilization, EPS synthesis, and secretion, along with its low virulence and antibiotic resistance levels, justify further research for its potential biotechnological application and possible use as a plant growth-promoting agent in the field. These findings suggest a unique genetic background in the P. agglomerans UADEC20 strain.

REMOVAL OF TOLUENE FROM TWO CONTRASTING SOILS, AN AGRICULTURAL SOIL AND AN ALKALINE SOIL

Hydrocarbon contamination cause serious environmental damage and human health problems, therefore, to resolve this problem has been proposed diversely remediation techniques friendly with the environment i.e. bioaugmentation, biostimulation, natural attenuation and phytoremediation. Among options, the phytoremediation causes minimum alterations to soil, low cost, it has proved good eff iciency and gained public acceptation. In the present study, the capacity of Mimosa pigra to restore a contaminated soil with both anthracene and phenanthrene was evaluated, along with the soil physicochemical changes due to both plant and contaminant presence in the soil. A silt-loam contaminated soil with 100 mg kg-1 (dry weight) anthracene and 200 mg kg-1 (dry weight) phenanthrene was used in all three treatments: Contaminated soil with M. pigra (C1), contaminated soil without M. pigra (C2), and not contaminated soil with M. pigra (C0) as control. After 70 days of experimentation both biomass and height of M. pigra was not affected due to soil contaminants. There was no difference among treatments for some physicochemical characteristics e.g. soil pH, electrolytic conductivity, soil-texture, and total nitrogen content throughout the experiment. M. pigra increased the soil water holding capacity after 50 and 70 days of the experiment, however, total organic carbon content was lower after 70 days compared to the control treatment. The higher contaminant removal rate was before 7 days of experimentation for all treatments. Anthracene and phenanthrene content were lower in treatments with the presence of M. pigra: 92% of phenanthrene and 80% of anthracene were removed in C1 while nearly 77% of phenanthrene and 60% of anthracene were removed in C2. This suggest a greater removal of contaminants using M. pigra. Total removal of contaminants was not achieved. However, M. pigra was able to accumulate both compounds, showing the M. pigra capability for bioremediation use in contaminated soils.

We studied three soils of the former lake Texcoco with different electrolytic conductivity (1.9 dS m⁻¹, 17.3 dS m⁻¹, and 33.4 dS m⁻¹) and pH (9.3, 10.4, and 10.3) amended with young maize plants and their neutral detergent fibre (NDF) fraction and aerobically incubated in the laboratory for 14 days while the soil bacterial community structure was monitored by means of 454-pyrosequencing of their 16S rRNA marker gene. We identified specific bacterial groups that showed adaptability to soil salinity, i.e., Prauseria in soil amended with young maize plants and Marinobacter in soil amended with NDF. An increase in soil salinity (17.3 dS m⁻¹, 33.4 dS m⁻¹) showed more bacterial genera enriched than soil with low salinity (1.9 dS m⁻¹). Functional prediction showed that members of Alfa-, Gamma-, and Deltaproteobacteria, which are known to adapt to extreme conditions, such as salinity and low nutrient soil content, were involved in the lignocellulose degradation, e.g., Marinimicrobium and Pseudomonas as cellulose degraders, and Halomonas and Methylobacterium as lignin degraders. This research showed that the taxonomic annotation and their functional prediction both highlighted keystone bacterial groups with the ability to degrade complex C-compounds, such as lignin and (hemi)cellulose, in the extreme saline-alkaline soil of the former Lake of Texcoco.

Background: Plant domestication is a continuous, multidirectional process that is directed via plant selection and management. In the current study we use Piper auritum, an aromatic plant frequently used in Mexican cuisine and for medicinal purpose, to characterize the domestication level using information about its cultural relevance, management practices and leaf traits differentiation in managed and ruderal populations. Questions: What is the level of domestication of the aromatic plant Piper auritum? Are there any morphological or phytochemical differences between home garden and ruderal populations? Studied species: Piper auritum, Kunth Study site and dates: Ten communities in eastern Yucatan, México, from 2019 to 2021. Methods: Fifty-three Semi-structured interviews were applied (72 % women and 28 % men). Morphological and phytochemical leaf traits were measured to test management effects using home garden and ruderal populations. Results: People interviewed knew P. auritum and its uses. Five culinary and 12 medicinal uses were registered. P. auritum is grown in homegardens and the main management activity is irrigation. The selection occurs at the leaf level according to their size and resistance. Home garden plants registered greater foliar area and hardness and decreased safrole, compared to ruderal. Conclusions: Piper auritum is widely known in the communities and has a variety of culinary and medicinal uses. Management is vital for its survival in home gardens, but the species germinates spontaneously and is not usually planted. We found differences in leaf traits in managed and unmanaged populations. With this evidence we propose that P. auritumis under incipient domestication.