Biology subjects

Maass, S.

Publications and source records attributed to Maass, S..

4 recordsLinked to original sources

bioRxiv2019

Peptide-based quorum sensing systems in Paenibacillus polymyxa

Paenibacillus polymyxa is an agriculturally important plant growth-promoting rhizobacterium. Many Paenibacillus species are known to be engaged in complex bacteria-bacteria and bacteria-host interactions, which in other species were shown to necessitate quorum sensing communication. However, to date no quorum sensing systems have been described in Paenibacillus. Here we show that the type strain P. polymyxa ATCC 842 encodes at least 16 peptide-based communication systems. Each of these systems is comprised of a pro-peptide that is secreted to the growth medium and processed to generate a mature short peptide. Each peptide has a cognate intracellular receptor of the RRNPP family, and we show that external addition of P. polymyxa communication peptides leads to reprogramming of the transcriptional response. We found that these quorum sensing systems are conserved across hundreds of species belonging to the Paenibacillaceae family, with some species encoding more than 25 different peptide-receptor pairs, representing a record number of quorum sensing systems encoded in a single genome.

microbiology↗

bioRxiv2019

Gradients in the cerebellar cortex enable Fourier-like transformation and improve storing capacity

Cerebellar granule cells (GCs) making up majority of all the neurons in the vertebrate brain, but heterogeneities among GCs and potential functional consequences are poorly understood. Here, we identified unexpected gradients in the biophysical properties of GCs. GCs closer to the white matter (inner-zone GCs) had higher firing thresholds and could sustain firing with larger current inputs. Dynamic clamp experiments showed that inner- and outer-zone GCs preferentially respond to high- and low-frequency mossy fiber inputs, respectively, enabling to disperse the mossy fiber input into its frequency components as performed by a Fourier transformation. Furthermore, inner-zone GCs have faster axonal conduction velocity and elicit faster synaptic potentials in Purkinje cells. Neuronal network modeling revealed that these gradients improve spike-timing precision of Purkinje cells and decrease the number of GCs required to learn spike-sequences. Thus, our study uncovers biophysical gradients in the cerebellar cortex enabling a Fourier-like transformation of mossy fiber inputs.

neuroscience↗

bioRxiv2019

Fungal traits important for soil aggregation

Soil health and sustainability is essential for ecosystem functioning and human well-being. Soil structure, the complex arrangement of soil into aggregates and pore spaces, is a key feature of soils under the influence of soil life. Soil biota, and among them filamentous saprobic fungi, have well-documented effects on soil aggregation. However, it is unclear what fungal properties, or traits, contribute to the overall positive effect on soil aggregation. So far, we lack a systematic investigation of a broad suite of fungal species for their trait expression and the relation of these traits to their soil aggregation capability.\n\nHere, we apply a trait-based approach to a set of 15 traits measured under standardized conditions on 31 fungal strains including Ascomycota, Basidiomycota and Mucoromycota, all isolated from the same soil.\n\nWe found a spectrum of soil aggregate formation capability ranging from neutral to positive and large differences in trait expression among strains. We identified biomass density (positive effects), leucine aminopeptidase activity (negative effects) and phylogeny as important modulators of fungal aggregate formation capability. Our results point to a typical suite of traits characterizing fungi that are good soil aggregators; this could inform screening for fungi to be used in biotechnological applications, and illustrates the power of employing a trait-based approach to unravel biological mechanisms of soil aggregation, which could now be extended to other organism groups.

ecology↗

bioRxiv2019

Posttranscriptional regulation of ribosomal and multiresistance genes by the bacterial leader peptide peTrpL

The ribosome-dependent attenuator located upstream of bacterial tryptophan biosynthesis genes harbors a small ORF trpL containing tryptophan codons. When tryptophan is available, efficient trpL translation causes transcription termination and release of the attenuator RNA rnTrpL. In Sinorhizobium meliloti, rnTrpL is a trans-acting sRNA. Here, we identified an evolutionary conserved function for the trpL-encoded 14-aa leader peptide peTrpL. Upon exposure to tetracycline, the cellular peTrpL levels were increased and rnTrpL was generated independently of tryptophan availability. Both peTrpL and rnTrpL were found to be involved in tetracycline-dependent destabilization of rplUrpmA mRNA encoding ribosomal proteins L21 and L27. We provide evidence for redirection of the sRNA rnTrpL from its antibiotic-independent target trpDC to rplUrpmA by formation of an antibiotic-dependent ribonucleoprotein complex (ARNP). ARNPs comprising peTrpL, rnTrpL, rplUrpmA and antisense RNA were also observed for other translation-inhibiting antibiotics, suggesting that bacteria evolved mechanisms to utilize antibiotics for mRNA destabilization.

microbiology↗