Minerals are known to influence microbial metabolism as nutrient sources or redox partners, yet whether chemically inert, non-nutritive minerals can regulate microbial physiology, and through what mechanisms, remains poorly understood. Here, we used transcriptomics to investigate the response of Enterococcus faecalis to Al2O3 and SiO2 particles spanning nanoscale to millimeter scale. Mineral exposure triggered extensive transcriptional reprogramming across hundreds of differentially expressed genes. Notably, a massive upregulation of iron acquisition genes (log2FC range from 3.8 to 4.2) concurrent with oxidative stress defenses (catalase, thiol peroxidase, and NADH oxidase) is suggestive of an "iron paradox," which is potentially attributable to mineral-mediated nutrient sequestration and steric hindrance of membrane transporters alongside interfacial reactive oxygen species generation. To adapt, E. faecalis orchestrated a coordinated metabolic shift, repressing serine catabolism (log2FC = -2.7) while investing nitrogen into glutathione biosynthesis (cystathionine synthase genes, log2FC = 3.7). Correlation analysis identified an ompR-sigV axis through which E. faecalis discriminates mineral particle size, with nanoscale particles eliciting stronger transcriptional responses than their larger counterparts. This stress response additionally upregulated virulence-associated genes and antibiotic resistance genes without direct antimicrobial selection pressure. These findings suggest that non-nutritive minerals shape microbial physiology through physical and surface-chemical cues independent of their nutritional value, highlighting the need for further exploration of the non-nutritional functions of minerals in microbial ecology.IMPORTANCEEven in the absence of utilizable nutrients, non-nutritive minerals such as Al2O3 and SiO2 can profoundly influence the transcriptional responses of Enterococcus faecalis. Using transcriptomic sequencing, we show that these inert minerals regulate microbial transcription, enhancing iron acquisition, oxidative stress repair, pathogenicity, and antibiotic resistance. Mineral-mediated transcriptional control is driven primarily by physical contact, surface chemistry, and particle size sensing, rather than conventional metabolic interactions. These findings identify inert minerals as signaling molecules that actively modulate microbial transcription, playing a proactive role in microbial evolution and environmental adaptation. This study redefines inert minerals as active carriers of transcriptional regulation, filling a critical gap in geomicrobiology and providing new insights into microbial environmental responses, biogeochemical cycling, and the mechanisms underlying microbial functional evolution and maintenance.

The inevitable introduction of human-associated microbes on Mars poses significant planetary protection risks, yet the survival potential of non-extremophiles under surface conditions remains ill-defined. We evaluated the resilience of three common gut bacteria—Enterococcus faecalis, Serratia liquefaciens, and Escherichia coli—under simulated Martian stressors including low pressure, CO₂-rich atmosphere, and perchlorate exposure, applied individually and in combination. Growth assays revealed a distinct tolerance hierarchy, with E. faecalis exhibiting the highest robustness, followed by E. coli and S. liquefaciens. Notably, combined stressors produced predominantly antagonistic effects across all three strains, indicating interactions that single-stressor assays may fail to capture. Transcriptomic profiling of E. faecalis under combined stress revealed a coordinated adaptive response involving conserved stress-response mechanisms rather than lineage-specific innovations. A concurrent potential shift toward enhanced surface adhesion and efflux activity, alongside suppression of acute virulence factors, raises biosafety concerns for crewed missions. Collectively, these results support a continuum model of microbial stress tolerance, in which persistence under extraterrestrial conditions does not require specialized extremophilic traits but can emerge from dynamic regulation of conserved systems, broadening the range of microorganisms relevant to forward-contamination risk.

Phosphorus (P) deficiency in soils is commonly addressed through phosphate fertilizers, yet millimeter-scale fertisphere dynamics governing fertilizer-soil interactions remain poorly understood, constraining P-use efficiency optimization. This study employed high-resolution chemical imaging to visualize P release patterns, pH dynamics, and acid phosphatase activity in acidic soil fertispheres of contrasting fertilizers: calcium hypophosphite (fast-acting) and apatite (slow-acting). Calcium hypophosphite exhibited rapid dissolution with peak P flux (442 pg cm-2 s-1) at patch edges within 24 h, coinciding with pH elevation that suppressed enzyme activity. Complete dissolution occurred within 48 h. Conversely, apatite released P steadily over 99 days (peak flux: 13.6 pg cm-2 s-1), with release zones shifting inward as H+ consumption generated alkalinization cores. Temporal analysis revealed a 22-day lag between P flux and pH maxima (R = 0.66). These mechanisms demonstrate the importance of matching fertilizer solubility with soil chemistry for precision P management, maximizing bioavailability while minimizing environmental losses.

Minerals are pivotal environmental factors influencing the adaptation and evolution of microbial communities. Conventional wisdom has long regarded the impact of minerals as a byproduct of their role in providing nutrients and energy to organisms, largely overlooking the significance of non-nutritive and energy-neutral mineral species. In this study, we explore the influence of minerals on microbial development in nutrient- and energy-rich media through a serial passage evolution experiment. Our results show both the inert mineral kaolinite and the energy/nutrient-rich olivine exert evident effects on the microorganisms. Both minerals induced substantial shifts in community structure. Notably, kaolinite and olivine selectively enriched specific taxa, including Acinetobacter and Clostridium. Metatranscriptomic analyses revealed substantial changes in gene expression, with both minerals enriching unique metabolic pathways. Interestingly, kaolinite specifically enriched pathways related to streptomycin biosynthesis. Both minerals stimulated the expression of antibiotic resistance genes (ARGs), particularly those associated with multidrug and macrolide resistance. Furthermore, both minerals induced the upregulation of genes involved in the degradation of complex organic matter, highlighting their potential role in soil carbon cycling. These findings underscore the intricate interplay between minerals and microbes, challenging the conventional notion that minerals function solely as material sources for organism growth.

Phosphorus (P) availability in soils is a critical environmental challenge affecting agricultural productivity and ecosystem health. Apatite minerals serve as a key P reservoir, yet their dissolution mechanisms at the microscale remain poorly understood due to technical limitations in directly observing mineral-solution interfaces. Here, we demonstrate an innovative dual-imaging approach that combines fluorescence-based pH monitoring with diffusive gradients in thin-films (DGT) to visualize apatite dissolution dynamics at a submillimeter resolution. Using the pH-sensitive fluorescent probe HPTS, we revealed distinct spatial patterns of pH increase at the apatite-solution interface after 2.5 h exposure in acidic solution (pH 6.0), with the highest pH observed within a 70 mu m interfacial layer. Concurrent DGT measurements showed P release peaked at 0.15 ng cm-2 s-1 at the interface, with radial diffusion patterns indicating reaction hotspots. This methodology provides unprecedented insights into the coupled dynamics of proton consumption and P release during mineral weathering. Our findings suggest that manipulating interfacial pH could enhance P mobilization from mineral sources, offering new strategies for optimizing nutrient availability in agricultural systems and understanding P cycling in natural environments.

Amorphous iron-arsenate precipitates are significant As sinks in natural and industrial settings and often serve as precursors to the crystallization of ferric arsenate minerals such as scorodite (FeAsO42H(2)O) and kankite (FeAsO43.5H(2)O). These amorphous phases have varied structures and compositions depending on the geochemical conditions under which they form but have not been well characterized except for the frequently encountered amorphous ferric arsenate (represented as AFe(III) in the present study). Here, we intend to characterize another phase, amorphous ferrous arsenate (AFe(II)), which is formed in partially oxidized Fe(II)-As(V) systems, and carry out a comparative study on the properties and related scorodite mineralization processes relative to those of AFe(III). We synthesized both AFe(II) and AFe(III), determined their compositions and structures, and finally examined the amorphous-crystalline phase transition processes leading to scorodite mineralization. Computed chemical formulas showed AFe(III) and AFe(II) can be represented by Fe(III)(0.99)AsO44.1H(2)O and Fe(III)(0.48)Fe(II)(0.43)(HAsO4)(0.7)(AsO4)(0.3)4.0H(2)O, respectively, with AFe(II) containing 47.3% Fe(II), as deduced from the pre-edge data of Fe K-edge X-ray absorption spectroscopy. Structurally, the Fe-O bond at 2.02 +/- 0.01 & Aring; in AFe(II) was significantly longer than that of 1.99 +/- 0.01 & Aring; in AFe(III) and scorodite. In addition, AFe(II) appeared to have a higher stability (slower kinetics of scorodite crystallization) under either atmospheric or aqueous conditions. Together with solution chemistry measurements, these findings suggest AFe(II) controls scorodite formation by limiting the occurrence of aqueous Fe3+ and retards the amorphous-scorodite phase transition compared to the case of AFe(III). These findings improve our understanding of iron arsenate system and may find industrial applications to arsenic sequestration via scorodite mineralization.

Woody peat is a valuable soil amendment, with its enhancement primarily relying on physical and chemical methods while biological treatment remains limited. This research investigated the biological compost of woody peat mediated by plant growth-promoting rhizobacteria (PGPR) strain Bacillus velezensis SQR9. The composted woody peat significantly increased cucumber biomass and height by 27-37 %, with dissolved organic carbon increasing 18.9-fold (to 69.61 mg/L) and humic acid content rising 3.7-fold (to 27.40 %). The relative abundance of Bacillus increased from undetectable level to 12.15 %. FT-ICR MS analysis revealed that 51.67 % of initial dissolved organic matters (DOM) underwent decomposition with formation of more bioavailable compounds. Network analysis revealed intricate correlations between microbial community and DOM subcategories, highlighting roles of key bacteria like Bacillus, Streptomyces and Thermosporothrix in DOM transformations. Moreover, sterilized treatment in plant experiments confirmed beneficial substances, rather than PGPR, played the dominant role in plant growth promotion. This study obtained a biofertilizer enriched with beneficial bacteria and humic acids, offering an environmentally sustainable approach to woody peat utilization in sustainable agriculture.

Minerals are fundamental yet underappreciated drivers of microbial ecology. Traditionally viewed as passive nutrient sources or inert scaffolds, their broader ecological roles remain poorly defined. This study investigates the evolutionary influence of substrates (minerals and rocks) on soil bacterial communities through serial passage evolution experiments. Soil-derived microbial consortia from three distinct locations were exposed to nutritive (olivine, granite, diorite) and non-nutritive (quartz, kaolinite, montmorillonite) substrates under nutrient-rich conditions to isolate substrate-specific effects. Results revealed systemic variations of community structure across all treatments, characterized by elevated Firmicutes/Bacteroidetes ratio and taxonomic changes predominantly driven by rare taxa. These discoveries indicate that, under the influence of substrates, the communities shifted toward ones that preferentially utilize more labile carbon. Crucially, the acute responsiveness of rare taxa to mineral-induced environmental selection suggests that, although abundant taxa appeared to maintain core community functions, the rare biosphere facilitated niche specialization and functional diversification. These findings position minerals as dynamic drivers of microbial ecology and evolution, highlighting the mineralosphere as a critical microhabitat where abiotic properties govern biodiversity, functional redundancy, and evolutionary innovation in soil ecosystems. IMPORTANCE:Even under nutrient-rich conditions, non-nutritive and chemically inert minerals, exemplified by quartz, actively reshape microbial community assembly. Through controlled serial-passage experiments, we show that distinct substrates selectively enrich rare biosphere members that expand functional potential and seed adaptation, while dominant taxa sustain core processes. These results reveal that mineral surface properties and physical interfaces, rather than nutrient supply, govern microbial diversification and evolutionary trajectories. Accordingly, the mineralosphere emerges as a dynamic microhabitat where abiotic complexity regulates biodiversity, metabolism, and long-term community succession. This reframes minerals and rocks as active ecological and evolutionary agents, bridging geomicrobiology and evolutionary ecology, with implications for soil health, biogeochemical cycling, and the origin and maintenance of microbial diversity.

Rhizosphere is a soil volume of high spatio-temporal heterogeneity and intensive plant-soil-microbial interactions, for which visualization and process quantification is of highest scientific and applied relevance, but still very challenging. A novel methodology for quick assessment of two-dimensional distribution of available phosphorus (P) in rhizosphere was suggested, tested, and development up to the application platform. Available P was firstly trapped by an in-situ diffusive gradients in thin-films (DGT) sampler with precipitated zirconia as the binding gel, and subsequently, the loaded gel was analyzed with an optimized colorimetric imaging densitometry (CID). The imaging platform was established linking: i) DGT, ii) planar optode, and iii) soil zymography techniques to simultaneously determine available P, oxygen, and acid phosphatase in rhizosphere at sub-millimeter spatial scales. The DGT identified available P level in rice rhizosphere were spatially overlapping to the localized redox hotspots and phosphatase activity. The spatial relationship between available P and acid phosphatase activity was dependent on root development. The root radial oxygen loss (ROL) remained active during the experimental observations (2-3 days), while a flux of available P of 10 pg cm-2 s-1 was visualized within 2-3 mm of roots, confirming the correlative response of rice roots to oxygen secretion and P uptake. Summarizing, the established imaging platform is suitable to capture spatial heterogeneity and temporal dynamics of root activities, nutrient bioavailability, ROL and enzyme activities in rhizosphere.

Methanogenic archaea are main contributors to methane emissions, and thus play a crucial role in carbon cycling and global warming. Until recently, methanogens were confined to the phylum Euryarchaeota, but metagenomic studies revealed the presence of genes encoding the methyl coenzyme M reductase complex in other archaeal clades, thereby opening up the premise that methanogenesis is taxonomically more widespread. Nevertheless, laboratory cultivation of these non-Euryarchaeal methanogens was missing to allow the study of their physiology and to corroborate their potential methanogenic capability. Here we describe a thermophilic co-culture from an oil field, containing a single archaeon (strain LWZ-6) belonging to the proposed order Candidatus Verstraetearchaeia, together with a H2-producing Acetomicrobium sp. CY-2. Strain LWZ-6, for which we propose the name Verstraetearchaeum methanopetracarbonis, is a H2-dependent methylotrophic methanogen. Although previous metagenomic studies speculated on the fermentative potential of Verstraetearchaeial methanogens, strain LWZ-6 does not ferment sugars, peptides, and amino acids. Its energy metabolism is linked to methanogenesis, with methanol and monomethylamine as electron acceptors and H2 as electron donor. Comparative (meta)genome analysis revealed that H2-dependent methylotrophic methanogenesis is a shared trait among Verstraetearchaeia. Our findings corroborate that the diversity of methanogens expands beyond the classical Euryarchaeota and change our current conception of the global carbon cycle.

Candidate bacterial phylum CSP1-3 has not been cultivated and is poorly understood. Here, we analyzed 112 CSP1-3 metagenome-assembled genomes and showed they are likely facultative anaerobes, with 3 of 5 families encoding autotrophy through the reductive glycine pathway (RGP), Wood-Ljungdahl pathway (WLP) or Calvin-Benson-Bassham (CBB), with hydrogen or sulfide as electron donors. Chemoautotrophic enrichments from hot spring sediments and fluorescence in situ hybridization revealed enrichment of six CSP1-3 genera, and both transcribed genes and DNA-stable isotope probing were consistent with proposed chemoautotrophic metabolisms. Ancestral state reconstructions showed that the ancestors of phylum CSP1-3 may have been acetogens that were autotrophic via the RGP, whereas the WLP and CBB were acquired by horizontal gene transfer. Our results reveal that CSP1-3 is a widely distributed phylum with the potential to contribute to the cycling of carbon, sulfur and nitrogen. The name Sysuimicrobiota phy. nov. is proposed.

Soil organic carbon (SOC) is the largest terrestrial carbon (C) pool and is vulnerable to climate and land-use changes. Promoting the stabilization of SOC will reduce climate change-induced C losses. Mineral-associated organic carbon (MAOC), formed by the association of organic carbon with silt- and clay-sized minerals, is the major stabilized SOC fraction and key to sustaining soil health and mitigating climate change. However, the role of silt and clay in MAOC formation remains unclear in dryland ecosystems where microbes and plants are frequently under water stress. The current paradigm assumes that the main role of silt and clay is to adsorb and aggregate organic compounds. In a semi-arid environment, using a naturally occurring gradient of increasing soil silt and clay content partially due to aeolian dust inputs, we show that silt and clay also enhanced microbial decomposition of plant C inputs and microbial turnover, increasing microbial C inclusion into the MAOC pool. Finer-textured soils had higher soil water availability and higher volume of habitat available to microorganisms. The enhanced microbial processing interacted with changes in plant C inputs to further control the relative contribution of MAOC to SOC. Our results suggest SOC models should include soil textural effects on microbial activities and microbial C production in addition to physical protection of SOC. Our study also suggests that aeolian dust inputs can increase soil silt and clay contents and improve nutrient availability in dryland ecosystems, potentially mitigating the SOC loss under climate change and increasing the resilience of ecosystems to drought.

Joint toxicity of organic-metal co-contamination can vary depending on organisms, toxicants, and even the sequence of exposure. This study examines how the combined toxicity of aniline (An) and cadmium (Cd) to soil bacteria in microcosms changes when the order of contaminant introduction is altered. Through analyzing biodiversity, molecular ecological network, functional redundancy, functional genes and pathways, we find the treatment of Cd followed by An brings about the strongest adverse impact to the bacterial consortium, followed by the reverse-ordered exposure and the simple mixture of the two chemicals. On the level of individual organisms, exposure sequence also affects the bacteria that are otherwise resistant to the standalone toxicity of both An and Cd. The dynamic behavior of aniline-cadmium composite is interpreted by considering the tolerance of organisms to individual chemicals, the interactions of the two toxicants, the recovery time, as well as the priority effect. The overall effect of the composite contamination is conceptualized by treating the chemicals as environmental filters screening the growth of the community.

Background Plants show developmental plasticity with variations in environmental nutrients. Considering low-cost rock dust has been identified as a potential alternative to artificial fertilizers for more sustainable agriculture, the growth responses of Arabidopsis seedlings on three rock meals (basalt, granite, and marlstone) were examined for the different foraging behavior, biomass accumulation, and root architecture. Results Compared to ½ MS medium, basalt and granite meal increased primary root length by 13% and 38%, respectively, but marlstone caused a 66% decrease, and they all drastically reduced initiation and elongation of lateral roots but lengthened root hairs. Simultaneous supply of organic nutrients and trace elements increased fresh weight due to the increased length of primary roots and root hairs. When nitrogen (N), phosphorus (P), and potassium (K) were supplied individually, N proved most effective in improving fresh weight of seedlings growing on basalt and granite, whereas K, followed by P, was most effective for those growing on marlstone. Unexpectedly, the addition of N to marlstone negatively affected seedling growth, which was associated with repressed auxin biosynthesis in roots. Conclusions Our data indicate that plants can recognize and adapt to complex mineral deficiency by adjusting hormonal homeostasis to achieve environmental sensitivity and developmental plasticity, which provide a basis for ecologically sound and sustainable strategies to maximize the use of natural resources and reduce the production of artificial fertilizers.

As productive and essential ecosystems, coastal wetlands have experienced increased environmental impacts such as saltwater intrusion and eutrophication, resulting in significant shifts in microbially mediated ecosystem functions, such as carbon sequestration and nutrient transformations. The soil microbial respiration, a primary process in the transfer of carbon from soil to the atmosphere, is susceptible to environmental changes. However, studies on how salinity affects soil microbial respiration in coastal wetlands have not been fully explored. Soil samples were systematically collected from divergent sampling sites covering medium- and extremely-saline wetlands along a river-estuary-coast continuum to investigate mechanisms controlling soil microbial respiration in coastal wetlands. According to the results, the microbial biomass and carbon-related extracellular enzyme activities were significantly lower in extremely saline (ECe >15 ds m(-1), ES) than medium and highly saline soils (ECe <15 ds m(-1), MHS) (p < 0.05), indicating a suppressive effect of salinity on soil microbiota. Meanwhile, high-salinity soils had lower vector length and soil microbial respiration rates, suggesting that soils with low carbon limitation might cause less carbon loss under higher salinity environments. Moreover, it was showed that increased available phosphorus could alleviate microbial carbon limitations. Changes in the microbial functional community demonstrated that the microbial community in favor of metabolic mediates and secondary metabolites substrates (regarded as labile substrates) were more sensitive to salinity. The partial least square path modeling further confirmed that microbial nutrient limitation and microbial biomass contribute more directly to promoting soil microbial respiration. These results have substantial implications for elucidating carbon dynamics in coastal wetlands ecosystems under increased nutrient discharge and sea-level rise.

Cadmium (Cd) and aniline frequently co-occur in industrial settings but have rarely been addressed as composite toxicants in terms of the overall toxicity despite extensive knowledge of the environmental impact of each individual pollutant. In this study, we attempt to assess the relation of individual and combined toxic effects of Cd and aniline using a bacterial consortium cultured from soils as a model system. Results showed that the consortial bacteria exhibited drastically stronger tolerance to stand-alone Cd and aniline in comparison to literature data acquired from single species studies. When occurring simultaneously, the joint toxicity displayed a concentration-dependent behavior that wasn't anticipated based on individual chemical tests. Specifically, additive effects manifested with Cd and aniline at their IC10s, but changed to synergistic when the concentrations increased to IC20, and finally transitioned into antagonistic at IC30s and beyond. In addition, co-occurring aniline appeared to have retarded the cellular accumulation of Cd while increasing the enzymatic activities of superoxide dismutase and catalase relative to that in Cd-alone treatments. Finally, the bacterial community experienced distinct compositional changes under solo and combined toxicities with several genera exhibiting inconsistent behavior between treatments of single and composite toxicants. Findings from this study highlight the complexity of bacterial response to composite pollutions and point to the need for more comprehensive references in risk and toxicology assessment at multi-chemical contamination sites.

Coastal wetlands contribute to the mitigation of climate change through the sequestration of "blue carbon". Microbial necromass, lignin, and glycoproteins (i.e., glomalin-related soil proteins (GRSP)), as important components of soil organic carbon (SOC), are sensitive to environmental change. However, their contributions to blue carbon formation and the underlying factors remain largely unresolved. To address this paucity of knowledge, we investigated their contributions to blue carbon formation along a salinity gradient in coastal marshes. Our results revealed decreasing contributions of microbial necromass and lignin to blue carbon as the salinity increased, while GRSP showed an opposite trend. Using random forest models, we showed that their contributions to SOC were dependent on microbial biomass and resource stoichiometry. In N-limited saline soils, contributions of microbial necromass to SOC decreased due to increased N-acquisition enzyme activity. Decreases in lignin contributions were linked to reduced mineral protection offered by short-range-ordered Fe (Fe-SRO). Partial least-squares path modeling (PLS-PM) further indicated that GRSP could increase microbial necromass and lignin formation by enhancing mineral protection. Our findings have implications for improving the accumulation of refractory and mineral-bound organic matter in coastal wetlands, considering the current scenario of heightened nutrient discharge and sea-level rise.

Despite the consensus that keeping global temperature rise within 1.5 °C above pre-industrial level by 2100 reduces the chance for climate change to reach the point of no return, the newest Intergovernmental Panel on Climate Change (IPCC) report warns that the existing commitment of greenhouse gas emission reduction is only enough to contain the warming to 3–4 °C by 2100. The harsh reality not only calls for speedier deployment of existing CO2 reduction technologies but demands development of more cost-efficient carbon removal strategies. Here we report an ocean alkalinity-based CO2 sequestration scheme, taking advantage of proton consumption during nitrate assimilation by marine photosynthetic microbes, and the ensuing enhancement of seawater CO2 absorption. Benchtop experiments using a native marine phytoplankton community confirmed pH elevation from ~8.2 to ~10.2 in seawater, within 3–5 days of microbial culture in nitrate-containing media. The alkaline condition was able to sustain at continued nutrient supply but reverted to normalcy (pH ~8.2–8.4) once the biomass was removed. Measurements of δ13C in the dissolved inorganic carbon revealed a significant atmospheric CO2 contribution to the carbonate alkalinity in the experimental seawater, confirming the occurrence of direct carbon dioxide capture from the air. Thermodynamic calculation shows a theoretical carbon removal rate of ~0.13 mol CO2/L seawater, if the seawater pH is allowed to decrease from 10.2 to 8.2. A cost analysis (using a standard bioreactor wastewater treatment plant as a template for CO2 trapping, and a modified moving-bed biofilm reactor for nitrate recycling) indicated that a 1 Mt CO2/year operation is able to perform at a cost of ~$40/tCO2, 2.5–5.5 times cheaper than that offered by any of the currently available direct air capture technologies, and more in line with the price of $25–30/tCO2 suggested for rapid deployment of large-scale CCS systems.

Pharmacolite (CaHAsO4·2H2O) mineralization is an important process controlling arsenate mobility in carbonate areas but is poorly understood in terms of crystallization mechanism and kinetics. The present study intends to investigate pharmacolite formation initiated by heterogenous nucleation through in situ observations of the mineral–water interface. Experiments were performed by exposing gypsum substrate to solutions supersaturated with respect to pharmacolite followed by atomic force microscopy imaging to record changes in surface morphology and topography. The data are used to determine growth mode, step speed, and the rate of step birth. Experimental results show the crystallization is achieved by direction-specific mono-molecular layer growth via 2D surface nucleation or spiral hillock development in accord with the classical crystallization model. Subsequent theoretical analyses allow to determine step energies and kinetic coefficients in major growth directions on (0 1 0) and indicate that [0 0 1] steps are energetically the most stable and morphologically the most prominent while [1 0 0] and [1 0 1] steps are controlled either by thermodynamic or kinetics. Gypsum plays an important role in aiding pharmacolite formation through epitaxy as the two minerals share a range of structural commonalities. The notably reduced supersaturation needed in substrate-assisted pharmacolite crystallization relative to bulk solution nucleation suggests gypsum may significantly reduce the energy barrier for the mineralization reactions and hence may find applications in As remediation practice.