Biology subjects

Perez, A. J.

Publications and source records attributed to Perez, A. J..

5 recordsLinked to original sources

bioRxiv2026

Assessing pollinator community recovery in restored agroecosystems using the recovery debt framework

Recovery debt (RD) quantifies the interim deficit of biodiversity and function during the recovery process after disturbance. Unlike typical recovery indices derived from data on experimental-control comparisons, RD further considers the target (reference) biodiversity level, modelling the rate at which it is approached over time. However, the application of the RD approach to active restoration has not been explicitly implemented to date. Here, we extend the RD framework to evaluate active ecological restoration in agricultural systems, defining the onset of recovery as the shift from intensive to wildlife-friendly management. We applied this approach to assess short-term pollinator recovery in 14 olive groves across a gradient of farming intensification and landscape complexity in southern Spain. Restoration actions included adopting low-intensity ground cover management and actively restoring field margins. At one, three, and five years post-restoration, we assessed community responses by quantifying bee abundance, species richness, plant-bee network properties, and flower visitation rates. Reference systems were defined by olive groves in complex landscapes with low-intensity herb cover management and organic farming practices. Following restoration, the RD of bee abundance decreased from 71% to 55%. We found no significant effects of pre-intervention agricultural management on RD. Instead, across sites, the reduction of the RD (i.e., recovery) of bee abundance, richness, network connectance and flower visitation rate was strongly mediated by the availability of high-quality semi-natural areas in the surrounding landscape and by the ecological contrast created by restoration interventions at both the farm and floral patch levels. RD for other network metrics showed no significant pattern of variation. Our study demonstrates that wildlife-friendly management and targeted habitat restoration can rapidly reduce recovery debt for bee abundance and function in permanent agroecosystems. However, the recovery of more complex interaction-network properties likely requires longer timescales.

ecology↗

bioRxiv2024

Elongasome core proteins and class A PBP1a display zonal, processive movement at the midcell of Streptococcus pneumoniae

Ovoid-shaped bacteria, such as Streptococcus pneumoniae (pneumococcus), have two spatially separated peptidoglycan (PG) synthase nanomachines that locate zonally to the midcell of dividing cells. The septal PG synthase bPBP2x:FtsW closes the septum of dividing pneumococcal cells, whereas the elongasome located on the outer edge of the septal annulus synthesizes peripheral PG outward. We showed previously by sm-TIRFm that the septal PG synthase moves circumferentially at midcell, driven by PG synthesis and not by FtsZ treadmilling. The pneumococcal elongasome consists of the PG synthase bPBP2b:RodA, regulators MreC, MreD, and RodZ, but not MreB, and genetically associated proteins Class A aPBP1a and muramidase MpgA. Given its zonal location separate from FtsZ, it was of considerable interest to determine the dynamics of proteins in the pneumococcal elongasome. We found that bPBP2b, RodA, and MreC move circumferentially with the same velocities and durations at midcell, driven by PG synthesis. However, outside of the midcell zone, the majority of these elongasome proteins move diffusively over the entire surface of cells. Depletion of MreC resulted in loss of circumferential movement of bPBP2b, and bPBP2b and RodA require each other for localization and circumferential movement. Notably, a fraction of aPBP1a molecules also moved circumferentially at midcell with velocities similar to those of components of the core elongasome, but for shorter durations. Other aPBP1a molecules were static at midcell or diffusing over cell bodies. Last, MpgA displayed non-processive, subdiffusive motion that was largely confined to the midcell region and less frequently detected over the cell body. SIGNIFICANCEThis paper reports three types of single-molecule motions of PG synthesis proteins in the ovoid-shaped, pathogenic bacterium Streptococcus pneumoniae, not reported previously in other bacteria. The core elongasome exhibits zonal, circumferential motion in the absence of MreB filaments, independent of FtsZ treadmilling or the processive movement of the septal PG synthase. Class A aPBP1a also moves processively at midcell, but is not a persistent component of the core elongasome. These types of motions have implications for the functions of these PG synthases and indicate that processive motion in pneumococcus follows spatially separate tracks, possibly reflective of PG structure. In contrast, the MpgA muramidase displays a different kind of subdiffusive motion that is largely confined to midcell by an unknown mechanism.

microbiology↗

bioRxiv2023

Chromosomal Duplications of MurZ (MurA2) or MurA (MurA1), Amino Acid Substitutions in MurZ (MurA2), and Absence of KhpAB Obviate the Requirement for Protein Phosphorylation in Streptococcus pneumoniae D39

GpsB links peptidoglycan synthases to other proteins that determine the shape of the respiratory pathogen Streptococcus pneumoniae (pneumococcus; Spn) and other low-GC Gram-positive bacteria. GpsB is also required for phosphorylation of proteins by the essential StkP(Spn) Ser/Thr protein kinase. Here we report three classes of frequently arising chromosomal duplications ({approx}21-176 genes) containing murZ (MurZ-family homolog of MurA) or murA that suppress {Delta}gpsB or {Delta}stkP. These duplications arose from three different repeated sequences and demonstrate the facility of pneumococcus to modulate gene dosage of numerous genes. Overproduction of MurZ or MurA alone or overexpression of MurZ caused by {Delta}khpAB mutations suppressed {Delta}gpsB or {Delta}stkP phenotypes to varying extents. {Delta}gpsB and {Delta}stkP were also suppressed by MurZ amino-acid changes distant from the active site, including one in commonly studied laboratory strains, and by truncation or deletion of the homolog of IreB(ReoM). Unlike in other Gram-positive bacteria, MurZ is predominant to MurA in pneumococcal cells. However, {Delta}gpsB and {Delta}stkP were not suppressed by {Delta}clpCP, which did not alter MurZ or MurA amounts. These results support a model in which regulation of MurZ and MurA activity, likely by IreB(Spn), is the only essential requirement for protein phosphorylation in exponentially growing D39 pneumococcal cells.

microbiology↗

bioRxiv2020

Organization of Peptidoglycan Synthesis in Nodes and Separate Rings at Different Stages of Cell Division of Streptococcus pneumoniae

Bacterial peptidoglycan (PG) synthesis requires strict spatial and temporal organization to reproduce specific cell shapes. In the ovoid-shaped, pathogenic bacterium Streptococcus pneumoniae (Spn), septal and peripheral (sidewall-like) PG synthesis occur simultaneously at midcell. To uncover the organization of proteins and activities that carry out these two modes of PG synthesis, we examined Spn cells vertically oriented onto their poles to image the division plane at the high lateral resolution of 3D-SIM (structured-illumination microscopy). Using fluorescent D-amino acid (FDAA) probes, we show that areas of new transpeptidase (TP) activity catalyzed by penicillin-binding proteins (PBPs) separate into a pair of concentric rings early in division, representing peripheral PG (pPG) synthesis (outer ring) and the leading-edge (inner ring) of septal PG (sPG) synthesis. Fluorescently tagged PBP2x or FtsZ locate primarily to the inner FDAA-marked ring, whereas PBP2b and FtsX remain in the outer ring, suggesting roles in sPG or pPG synthesis, respectively. Short pulses of FDAA labeling revealed an arrangement of separate regularly spaced "nodes" of TP activity around the division site of predivisional cells. Control experiments in wild-type and mutant strains support the interpretation of nodal spacing of TP activity, and statistical analysis confirmed that the number of nodes correlates with different ring diameters. This nodal pattern of FDAA labeling is conserved in other ovoid-shaped species. Tagged PBP2x, PBP2b, and FtsX proteins also exhibited nodal patterns with spacing comparable to that of FDAA labeling. Together, these results reveal a highly ordered PG synthesis apparatus in ovococcal bacteria at different stages of division. SIGNIFICANCEThe spatial organization of PBPs and their TP activity at division septa is not well understood. In some bacteria, TP activity and PBP localization seem to be nodal (also called punctate), whereas in other bacteria, discrete foci of PBP activity are infrequently or not observed. Here we report two basic properties of the organization of PBPs and TP activity in the ovoid-shaped bacterium Spn. First, there is distinct spatial separation of the sPG machine, including FtsZ, from the pPG synthesis machine at the midcell of dividing Spn cells. Second, in predivisional cells, PBPs and TP activity are organized heterogeneously into regularly spaced nodes, whose number and dynamic distribution are likely driven by the PG synthesis of PBP:SEDS complexes.

microbiology↗

bioRxiv2018

Movement Dynamics of Divisome and Penicillin-Binding Proteins (PBPs) in Cells of Streptococcus pneumoniae

Bacterial cell division and peptidoglycan (PG) synthesis are orchestrated by the coordinated dynamic movement of essential protein complexes. Recent studies show that bidirectional treadmilling of FtsZ filaments/bundles is tightly coupled to and limiting for both septal PG synthesis and septum closure in some bacteria, but not in others. Here we report the dynamics of FtsZ movement leading to septal and equatorial ring formation in the ovoid-shaped pathogen, Streptococcus pneumoniae (Spn). Conventional and single-molecule total internal reflection fluorescence microscopy (TIRFm) showed that nascent rings of FtsZ and its anchoring and stabilizing proteins FtsA and EzrA move out from mature septal rings coincident with MapZ rings early in cell division. This mode of continuous nascent ring movement contrasts with a failsafe streaming mechanism of FtsZ/FtsA/EzrA observed in a {Delta}mapZ mutant and another Streptococcus species. This analysis also provides several parameters of FtsZ treadmilling in nascent and mature rings, including treadmilling velocity in wild-type cells and ftsZ(GTPase) mutants, lifetimes of FtsZ subunits in filaments and of entire FtsZ filaments/bundles, and the processivity length of treadmilling of FtsZ filament/bundles. In addition, we delineated the motion of the septal PBP2x transpeptidase and its FtsW glycosyl transferase binding partner relative to FtsZ treadmilling in Spn cells. Five lines of evidence support the conclusion that movement of the bPBP2x:FtsW complex in septa depends on PG synthesis and not on FtsZ treadmilling. Together, these results support a model in which FtsZ dynamics and associations organize and distribute septal PG synthesis, but do not control its rate in Spn.\n\nSignificanceThis study answers two long-standing questions about FtsZ dynamics and its relationship to septal PG synthesis in Spn for the first time. In previous models, FtsZ concertedly moves from midcell septa to MapZ rings that have reached the equators of daughter cells. Instead, the results presented here show that FtsZ, FtsA, and EzrA filaments/bundles move continuously out from early septa as part of MapZ rings. In addition, this study establishes that the movement of bPBP2x:FtsW complexes in septal PG synthesis depends on and likely mirrors new PG synthesis and is not correlated with the treadmilling of FtsZ filaments/bundles. These findings are consistent with a mechanism where septal FtsZ rings organize directional movement of bPBP2x:FtsW complexes dependent on PG substrate availability.

microbiology↗