bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2021.03.08.434393

Hillslope geodiversity shapes ammonia-oxidizing communities and other microbial regulators in a semi-arid shrubland

Szitenberg, A.·Alexander-Shani, R.·Yizhak, H.·Stavi, I.
View original source ↗Export metadata ↓

Abstract

The determinants and consequences of drought-related shrub mortality were studied for over a decade, as a model for desertification processes, in a semi-arid long-term ecological research station. Recent studies have shown that geodiversity is an important spatial predictor of plant viability under extreme drought conditions. Homogeneous hillslopes, with a deep soil profile and lack of stoniness, could not support shrubs under long term drought conditions due to low water storage in their soil. Conversely, heterogeneous hillslopes, with shallow soil profiles and high stoniness, supported shrub communities under similar conditions, due to the comparatively greater soil-water content. In the current study, we investigated the effect of hillslope geodiversity on the soil microbial diversity. Using DNA metabarcoding, we found small but consistent differences in the microbial community compositions of the homogeneous and heterogeneous hillslopes; more ammonia oxidizing and reducing-sugar degrading bacteria are found in the homogeneous hillslopes, possibly dwindling the ammonia supply to shrubs. Additionally, based on functional metagenomic reconstruction, we suggest that homogeneous hillslopes have lower superoxide and antibiotics production, leading to reduced protection against pathogens. In fungi, we observed an increase in possible pathogens, at the expense of lichen forming fungi. Lichens are considered to support soil-water by slowly releasing intercepted raindrops. In conclusion, we show that not only plant-diversity but also microbial-diversity is shaped by geodiversity, and that the community shift in homogeneous hillslopes may further promote shrub mortality in this drought-prone, water limited ecosystem. HIGHLIGHTSO_LIHomogeneous hillslopes reduce soil water storage and increase aeration. C_LIO_LIAmmonia oxidizers and reducing-sugar degraders dwindle ammonia supply for plants. C_LIO_LIHomogenous hillslopes do not support moisture providing lichens. C_LIO_LIReduced antibiotics and superoxide secretion capacitate pathogens. C_LIO_LIGeodiversity facilitates microbial regulation during drought. C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/434393v2_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1503208org.highwire.dtl.DTLVardef@4c589org.highwire.dtl.DTLVardef@144d17dorg.highwire.dtl.DTLVardef@1159040_HPS_FORMAT_FIGEXP M_FIG C_FIG

Explore related subjects

microbiologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Szitenberg, A., Alexander-Shani, R., Yizhak, H., Stavi, I.. 2021-03-08. Hillslope geodiversity shapes ammonia-oxidizing communities and other microbial regulators in a semi-arid shrubland. https://doi.org/10.1101/2021.03.08.434393

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

A conserved cysteine-histidine-glutamate metal site identifies DUF501 (Rv1025), an essential uncharacterised protein family of Mycobacterium tuberculosis, as a candidate metalloenzyme and drug target

A substantial fraction of the Mycobacterium tuberculosis proteome remains functionally uncharacterised. Rv1025, a 155-residue protein carrying the domain of unknown function DUF501 (Pfam PF04417), is essential by transposon mutagenesis and vulnerable by CRISPR interference, an attractive but neglected drug target, yet has never been functionally described. The family (4,370 proteins, no Gene Ontology term, no solved structure) is uncharacterised across all organisms and essential in three Actinobacterial genera. A Foldseek search of the AlphaFold model against complete structural databases finds no significant homolog, indicating a novel fold. The operon eno-divIC-Rv1025-ppx2 is conserved across the Actinobacteria phylum, yet AlphaFold-Multimer finds no direct complex between Rv1025 and its neighbour DivIC. Instead, conservation across 8,700 homologous sequences reveals a near-invariant Cys113-His115-Glu59 cluster forming a pocket. Holo AlphaFold3 predictions with Zn, Fe and Mn confidently place a divalent metal on this triad at 2.25-2.47 A; mutating the triad relocates the metal, and an independent backbone-geometry predictor recovers the same site, confirming specificity. The triad is universal across the family: present in all 1,472 near-complete bacterial sequences of the Pfam alignment, with no non-conservative substitution among the 2,228 sequences examined, a defining feature of bacterial DUF501 rather than a mycobacterial peculiarity. We propose that DUF501 is a metal-binding protein and candidate metalloenzyme, the first functional hypothesis for this family, whose conserved, essential metal pocket is a promising drug target. As the predictions build on a conservation-defined site within a fully computational study, they are supportive rather than proof of metal occupancy and warrant experimental validation.

microbiology↗
bioRxiv2026

Mycoplasmal endosymbionts of Trichomonas vaginalis are associated with reduced risk for Chlamydia trachomatis endometrial infection in asymptomatic, coinfected, women.

Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis, the most common curable non-viral sexually transmitted infection, and Chlamydia trachomatis is a bacterial pathogen that can ascend to the upper genital tract and cause pelvic inflammatory disease, infertility, and ectopic pregnancy. T. vaginalis harbors bacterial endosymbionts, including Candidatus Malacoplasma girerdii, an obligate symbiont, and Metamycoplasma hominis, which can live freely or symbiotically. In a 16S rRNA sequencing study of the cervicovaginal microbiome of women at high risk for chlamydial infection, Ca. M. girerdii abundance was one of 13 features predicting lack of chlamydial spread to the endometrium, despite no direct association between T. vaginalis infection and reduced chlamydial ascension. Investigating the relationship between these microorganisms further, we found that T. vaginalis vaginal abundance correlated positively with chlamydial burden in women whose infection was confined to the cervix, while a nonsignificant inverse relationship was seen in women with endometrial spread. Among participants with high chlamydial burden, Ca. M. girerdii was detected exclusively in women without endometrial infection. Both endosymbionts trended toward more frequent detection, and higher abundance, in coinfected women without endometrial spread, while M. hominis abundance correlated strongly with T. vaginalis burden in this group. These findings suggest that mycoplasmal endosymbionts of T. vaginalis, rather than T. vaginalis itself, are microbial factors limiting chlamydial ascension, and point to a three-way interaction between parasite, endosymbiont, and bacterial pathogen that shapes upper genital tract C. trachomatis infection risk.

microbiology↗
bioRxiv2026

Understanding the physiological alterations of Vibrio cholerae upon exposure to L-ascorbic acid

The scourge of cholera remains a major global public health threat. It affects up to 4 million people worldwide and causes tens of thousands of deaths each year. The disease is experiencing a concerning resurgence in many parts of Africa, the Middle East, and Asia. To effectively tackle cholera and circumvent rising antimicrobial resistance, targeted biological and preventive approaches, complementing traditional rehydration, are urgently needed. In this regard, our group has demonstrated the efficacy of L-ascorbic acid in controlling the growth and pathogenesis of Vibrio cholerae in vitro. The present work further provides a mechanistic elucidation of the L-ascorbic acid-mediated physiological changes in V. cholerae and also bolsters such a non-antibiotic approach to control cholera.

microbiology↗