Researchers provide first insight into arbuscular mycorrhizal fungi found in desert habitats
Deserts fill a significant part of the Earth’s surface and continue to expand due to an effect of climate change.
Arbuscular mycorrhiza is a type of fungal root in which the symbiont fungus enters the root’s cortical cell of a vascular plant.
Mutualistic arbuscular mycorrhizal fungi may be important in plant roots, particularly in drought stressed environment such as deserts.
Researchers provide the characterization of the arbuscular mycorrhizal fungi found in several desert locations around the world.
Researchers utilized Illumina MiSeq and sequenced arbuscular mycorrhizal fungal DNA from desert soil samples in six different geographic locations.
Researchers recorded 50 arbuscular mycorrhizal fungal phylotypes.
Phylotype is an overall similarity used to classify several organisms into a group according to their phenetic relationship.
The most common family found was Glomeraceae.
Researchers also found Claroideoglomeraceae, Diversisporaceae, and Acaulosporaceae however, their frequencies and abundances were low.
The site with the highest diversity was in Israel’s Negev desert with 35 virtual taxa.
Sites in Argentina, Australia, Kazakhstan and United States were found to have lower richness and diversity.
Saudi Arabian desert which has harsh conditions yielded low richness with only three Diversispora virtual taxa.
Although the arbuscular mycorrhizal fungal taxa recorded in the desert were mostly ecological and geographically widespread, four out of the six sites constitute more desert-associated taxa than expected at random.
The phylogenetic/taxonomic composition of arbuscular mycorrhizal fungal communities was mostly driven by pH.
Data show that desert arbuscular mycorrhizal fungal community composition and diversity are dependent on ecological conditions.
Arbuscular mycorrhizal fungal community composition can also be related to harsh abiotic conditions.
Arbuscular mycorrhizal fungal virtual taxa present in soil samples were phylogenetically clustered than the global taxon pool.
Results suggest that desert fungal collections may have been shaped by non-random assembly mechanisms, particularly habitat filtering.
Climate change may likely trigger desertification in many locations and more research on arbuscular mycorrhizal fungi should be performed to understand ecosystem change.
Vasar, M., Davison, J., Sepp, S. K., Öpik, M., Moora, M., Koorem, K., Meng, Y., Oja, J., Akhmetzhanova, A. A., Al-Quraishy, S., Onipchenko, V. G., Cantero, J. J., Glassman, S. I., Hozzein, W. N., & Zobel, M. (2021). Arbuscular Mycorrhizal Fungal Communities in the Soils of Desert Habitats. Microorganisms, 9(2), 229. https://doi.org/10.3390/microorganisms9020229
New bacteria discovered in Southern California may be affiliating with cyanobacteria
Sediminibacterium is a member of Chitinophagaceae first described in 2008.
Sediminibacterium is a gram-negative bacterium and is closely related to Niabella and Terrimonas.
Sediminibacterium is motile and can be either obligate aerobes or facultative anaerobes.
A group of Southern California researchers led by Prof. Arun Sethuraman of San Diego State University and California State University San Marcos discovered the novel Sediminibacterium.
The discovery came after sequencing laboratory cultures of cyanobacteria from freshwater streams in Southern California.
The genome of Sediminibacterium that resides in the blue-green algal phycosphere was sequenced.
Phycosphere is a mucus region containing organic matter which surrounds a cyanobacterium.
Microalgae secrete a sugary substance into the phycosphere which can be used by bacterial colonizers.
Analysis revealed an almost complete genome that was placed within sediminibacterial clades.
Results also revealed that the new bacteria may have genes involved in a mutualistic/commensal relationship with cyanobacteria.
The study helps understand the relationship between sediminibacteria and cyanobacteria, and the discovered genome may be utilized for future research.
Sethuraman, A., Stancheva, R., Sanders, C., Caceres, L., Castro, D., Hausknecht-Buss, H., Henry, S., Johansen, H., Kasler, A., Lastor, S., Massaro, I., Mekuria, I., Moron-Solano, A., Read, N., Vengerova, G., Zhang, A., Zhang, X., & Read, B. (2022). Genome of a novel Sediminibacterium discovered in association with two species of freshwater cyanobacteria from streams in Southern California. G3 (Bethesda, Md.), jkac123. Advance online publication. https://doi.org/10.1093/g3journal/jkac123
Warmer temperature increases metabolic processes and cell division but lowers protein synthesis in soil microbes
Responses of soil microbes to global warming are important to conclude future soil-climate feedback; however, it is not well understood.
Researchers investigated microbial physiological responses to medium-term and long-term subarctic grassland soil warming of +6°C.
Medium-term is 8 years and long-term is more than 50 years.
Researchers observed indications for a community-wide increase in central metabolic pathways and cellular replication.
Additionally, researchers observed a reduction of bacterial protein biosynthesis machinery in the elevated temperature soils which occur at the same time with lower microbial biomass, RNA, and substrate content.
Researchers concluded that the increased reaction rates at higher temperatures and the reduction of substrates triggered ribosome reduction.
The ribosome is a macromolecular complex that carries protein synthesis.
Another study involving short-term warming experiment of +6°C at 6 weeks further supported the conclusion.
The reduction of protein biosynthesis machinery frees up energy and matter which allows soil microbes to continue a high metabolic process and cellular division even after years of increasing temperature.
 De Vos, Lobke; Van de Voorde, Babs; Van Daele, Lenny; Dubruel, Peter; Van Vlierberghe, Sandra (December 2021). “Poly(alkylene terephthalate)s: From current developments in synthetic strategies towards applications”. European Polymer Journal. 161: 110840. https://doi.org/10.1016/j.eurpolymj.2021.110840
Bacteria “vaccinate” themselves to protect from viral infection
Prokaryotes have developed various defense mechanisms against viruses.
CRISPR is one of the processes that protect prokaryotic organisms from viruses.
CRISPR allows bacteria to remember DNA from invading viruses and chop off viral DNA to stop the infection.
Researchers studied the relationship between two of the popular prokaryotic immune systems namely CRISPR and restriction-modification.
Both mechanisms utilize enzymes that cut a specific DNA sequence of the invading virus; however, CRISPR nucleases are programmed with phage-derived spacer sequences which are integrated into the CRISPR genetic position upon infection.
Researchers found restriction enzymes help in providing short-term defense which can be quickly overcome through methylation of the viral genome.
Methylation is a process by which a methyl group is added to DNA and inhibits gene expression.
Restriction enzymes can cut short DNA sequences so bacteria can utilize these DNA sequences soon after viral infection starts.
However, few other cells acquired spacer sequences from the cleavage site which moderate a strong type II-A CRISPR-Cas immune mechanism against the methylated virus.
This mechanism reminds us of the eukaryotic immune response in which the innate immunity provides a first short-term line of defense and also activates a second but stronger adaptive immune response.
Maguin, P., Varble, A., Modell, J. W., & Marraffini, L. A. (2022). Cleavage of viral DNA by restriction endonucleases stimulates the type II CRISPR-Cas immune response. Molecular cell, 82(5), 907–919.e7. https://doi.org/10.1016/j.molcel.2022.01.012
Microbes work together to form drug-tolerant communities
Microbial communities comprise cells with different metabolic capacities and may include auxotrophs.
Auxotroph is an organism, usually a mutant bacteria, that cannot synthesize substances needed for its growth and metabolism.
Researchers analyzed amino acid biosynthesis pathways in auxotroph from microbiome data of more than 12,000 natural microbial communities.
Researchers also examined the auxotrophic-prototrophic interactions in yeast communities.
Researchers discovered a mechanism that links auxotrophs to an increase in metabolic interactions and anti-microbial drug tolerance.
The auxotrophs have been observed to obtain altered metabolic flux distribution, export more metabolites, and as a result, enrich the community in metabolites.
Metabolites are intermediate or end-product substances produced by metabolism.
These capabilities observed from auxotrophs may be the consequence of the metabolic adaptations required to use specific metabolites.
Additionally, researchers observed that the increased metabolite exportation was correlated with the decrease in intracellular drug concentrations.
The reduction of intracellular drug concentration allows microbes to grow even at drug levels above minimal inhibitory concentrations.
Minimal inhibitory concentration is the lowest concentration of drugs that can inhibit the growth of bacteria.
Researchers demonstrated that an antifungal compound called azoles did not significantly eliminate yeast cells that use metabolites from a metabolically-enriched environment.
The results describe a mechanism that enhances our understanding of why cells are more tolerant to drug exposure when they metabolically interact.
Yu, J.S.L., Correia-Melo, C., Zorrilla, F. et al. Microbial communities form rich extracellular metabolomes that foster metabolic interactions and promote drug tolerance. Nat Microbiol (2022). https://doi.org/10.1038/s41564-022-01072-5
Blind cavefishes have larger red blood cells to survive in a low-oxygen habitat
Animals that thrive in extreme environments can be used to study adaptive evolution in response to different pressures.
One example of these pressures is reduced oxygen levels.
Environments with low oxygen are commonly found in subterranean and high-altitude regions.
Animals living in caves must also deal with starvation and the dark environment, both of which have been thoroughly studied as an important factor driving the evolution of traits related to caves.
Hypoxia, the state in which oxygen is lacking at the tissue level, does not receive much attention as an environmental pressure.
Researchers examined adaptive characteristics evolving in Mexican tetra, also known as the blind cavefish.
Mexican tetra is notable for having no eyes or pigment.
Mexican tetra has two forms, surface-dwelling, and cave-dwelling.
Additionally, researchers also identified other responses to hypoxia with the help of many natural and independently-colonized cave populations together with closely-related surface animals of the same species.
Researchers focused on a very important oxygen-carrier molecule called hemoglobin.
Researchers discovered that numerous cave populations had higher hemoglobin concentration which was proportional to the increase in red blood cell size of the cave-dwelling form compared to the surface-dwelling fish.
Interestingly, both cave and surface-dwelling fishes had similar concentrations of red blood cells which suggest that higher hemoglobin levels were not due to the rise of red blood cell count.
Researchers speculated that the larger-sized red blood cells in cavefish contain more hemoglobin.
The study reinforces the idea that cavefish have adapted to low oxygen environments through changes in both red blood cell size and hemoglobin production.
Boggs, T.E., Friedman, J.S. & Gross, J.B. Alterations to cavefish red blood cells provide evidence of adaptation to reduced subterranean oxygen. Sci Rep 12, 3735 (2022). https://doi.org/10.1038/s41598-022-07619-0
 Keene, A.; Yoshizawa, M.; McGaugh, S. (2016). Biology and Evolution of the Mexican Cavefish. pp. 68–69, 77–87. ISBN978-0-12-802148-4