The understanding of the functional role of aquatic bacteria in microbial food webs is largely dependent on methods applied to the direct visualization and enumeration of these organisms. While the ultrastructure of aquatic bacteria is still poorly known, routine observation of aquatic bacteria by light microscopy requires staining with fluorochromes, followed by filtration and direct counting on filter surfaces. Here, we used a new strategy to visualize and enumerate aquatic bacteria by light microscopy. By spinning water samples from varied tropical ecosystems in a cytocentrifuge, we found that bacteria firmly adhere to regular slides, can be stained by fluorochoromes with no background formation and fast enumerated. Significant correlations were found between the cytocentrifugation and filter-based methods. Moreover, preparations through cytocentrifugation were more adequate for bacterial viability evaluation than filter-based preparations. Transmission electron microscopic analyses revealed a morphological diversity of bacteria with different internal and external structures, such as large variation in the cell envelope and capsule thickness, and presence or not of thylakoid membranes. Our results demonstrate that aquatic bacteria represent an ultrastructurally diverse population and open avenues for easy handling/quantification and better visualization of bacteria by light microscopy without the need of filter membranes.

We report that lysosomal damage is a hitherto unknown inducer of stress granule (SG) formation and that the process termed membrane atg8ylation coordinates SG formation with mTOR inactivation during lysosomal stress. SGs were induced by lysosome-damaging agents including SARS-CoV-2ORF3a, Mycobacterium tuberculosis, and proteopathic tau. During damage, mammalian ATG8s directly interacted with the core SG proteins NUFIP2 and G3BP1. Atg8ylation was needed for their recruitment to damaged lysosomes independently of SG condensates whereupon NUFIP2 contributed to mTOR inactivation via the Ragulator–RagA/B complex. Thus, cells employ membrane atg8ylation to control and coordinate SG and mTOR responses to lysosomal damage.

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Until now, there has been neither an agreed-upon experimental model nor descriptors of the clinical symptoms that occur over the course of acute murine infection. The aim of this work is to use noninvasive methods to evaluate clinical signs in Swiss Webster mice that were experimentally infected with the Y strain of Trypanosoma cruzi during acute phase (Inf group). Infected mice showed evident clinical changes beginning in the second week of infection (wpi) when compared to the noninfected group (NI): (1) animals in hunched postures, closed eyes, lowered ears, peeling skin, increased piloerection, prostration, and social isolation; (2) significant decrease in body weight (Inf: 26.2 ± 2.6 g vs. NI: 34.2 ± 2.5 g) and in chow (1.5 ± 0.3 vs. 6.3 ± 0.5 mg) and water (2.4 ± 0.5 vs. 5.8 ± 0.7 ml) intake; (3) significant decrease of spontaneous activity as locomotor parameters: distance (0.64 ± 0.06 vs. 1.8 ± 0.13 m), velocity (1.9 ± 0.3 vs. 6.7 ± 1.5 cm/sec), and exploratory behavior by frequency (1.0 ± 0.5 vs. 5.7 ± 1.0 events) and duration (1.4 ± 0.3 vs. 5.1 ± 0.5 sec in central arena region); (4) significant increase in the PR (41.7 ± 8.7 vs. 27.6 ± 1.9 msec) and QT intervals (39.7 ± 2.0 vs. 27.5 ± 4.0 msec), and a decreased cardiac frequency (505 ± 52.8 vs. 774 ± 17.8 msec), showing a marked sinus bradycardia and an atrioventricular block. At 3 and 4 wpi, the surviving animals showed a tendency of recovery in body weight, food intake, locomotor activity, and exploratory interest. Through the use of noninvasive parameters, we were able to monitor the severity of the infection in individuals prior to death. Our perspective is the application of noninvasive methods to describe clinical signs over the course of acute infection complementing the preclinical evaluation of new agents, alone or in combination with benznidazole.

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