This review provides insights into cellulolytic bacteria present in global forest and agricultural soils over a period of 11 years. It delves into the study of soil-dwelling cellulolytic bacteria and the enzymes they produce, cellulases, which are crucial in both soil formation and the carbon cycle. Forests and agricultural activities are significant contributors to the production of lignocellulosic biomass. Forest ecosystems, which are key carbon sinks, contain 20–30% cellulose in their leaf litter. Concurrently, the agricultural sector generates approximately 998 million tons of lignocellulosic waste annually. Predominant genera include Bacillus, Pseudomonas, Stenotrophomonas, and Streptomyces in forests and Bacillus, Streptomyces, Pseudomonas, and Arthrobacter in agricultural soils. Selection of cellulolytic bacteria is based on their hydrolysis ability, using artificial cellulose media and dyes like Congo red or iodine for detection. Some studies also measure cellulolytic activity in vitro. Notably, bacterial cellulose hydrolysis capability may not align with their cellulolytic enzyme production. Enzymes such as GH1, GH3, GH5, GH6, GH8, GH9, GH10, GH12, GH26, GH44, GH45, GH48, GH51, GH74, GH124, and GH148 are crucial, particularly GH48 for crystalline cellulose degradation. Conversely, bacteria with GH5 and GH9 often fail to degrade crystalline cellulose. Accurate identification of cellulolytic bacteria necessitates comprehensive genomic analysis, supplemented by additional proteomic and transcriptomic techniques. Cellulases, known for degrading cellulose, are also significant in healthcare, food, textiles, bio-washing, bleaching, paper production, ink removal, and biotechnology, emphasizing the importance of discovering novel cellulolytic strains in soil.

Arid and semi-arid soils display low productivity due to abiotic stress associated with drought and salinity. Halobacteria can increase the yield of crops grown under these types of stress. These bacteria thrive across a wide salinity range (1–25% NaCl) and also in the absence of NaCl and have direct and indirect mechanisms that promote plant growth. This review summarizes studies conducted over the past five years that have assessed the effect of halobacteria on plants and soil fertility. The criteria used in the selection of halobacteria were also reviewed. Few studies have assessed the impact of halobacteria on soil fertility. The selection of halobacteria has been based on a qualitative criterion considering the morphology of colonies grown in media enriched with salts, mainly Na⁺. Not all bacteria growing in salt-enriched media are capable of capturing Na⁺ ions. Therefore, a quantitative criterion should be applied for the selection of halobacteria, which could be their ability to capture Na⁺ ions in vitro. This, together with the assessment of the effect of halobacteria on soil fertility, may largely contribute to the recovery of saline soils.

The rhizosphere microbiota of arid plants plays a crucial role in adaptation to environmental stress. However, few studies have characterized microorganisms associated with Agave species and their contribution to resilience against salinity and drought. This study aimed to isolate and characterize halotolerant bacteria from the rhizosphere of Agave potatorum Zucc from two different sites and evaluate their in vitro Na⁺ sequestration, desiccation resistance, and phytohormone production. These traits were compared with those of halotolerant bacteria isolated from a highly saline soil at a third site. Bacteria were obtained through serial dilutions and cultured on R2A plates supplemented with varying NaCl concentrations. The most efficient Na⁺-sequestering isolates underwent an 18-day desiccation assay, and their production of indole-3-acetic acid (IAA) and gibberellic acid (GA₃) was quantified. Among the 48 halotolerant isolates obtained, 7 (SM1, SM10, SPM5, SM7, SM19, VZ9, and SPM1) exhibited the highest Na⁺ sequestration efficiency. Among these isolates, SM1 exhibited the highest in vitro Na⁺ sequestration capacity (10.74 μg L⁻¹, p < 0.05). SM1 and SPM1 demonstrated the greatest desiccation resistance, at 88.39% and 83.05%, respectively. Additionally, SM7 produced the highest levels of IAA (13.69 μg mL⁻¹, p < 0.05), while SM1 exhibited the highest GA₃ production (1285.38 μg mL⁻¹, p < 0.05). Based on these characteristics, isolates SPM1 and SM1 exhibited the highest efficiency in tolerating drought and salinity stress. However, isolate SPM1 may colonize the rhizosphere of A. potatorum more effectively, likely due to its adaptation as a native isolate to the edaphic and environmental conditions in which this agave thrives. Molecular identification confirmed that the isolates belong to the genera Kosakonia, Priestia, Streptomyces, Bacillus, Stutzerimonas, Pseudomonas, and Exiguobacterium. This study highlights the diversity of halotolerant bacteria in the rhizosphere of A. potatorum and their potential as bioinoculants for enhancing soil fertility and restoring degraded soils.