Biology subjects

Goldberg, D. A.

Publications and source records attributed to Goldberg, D. A..

4 recordsLinked to original sources

bioRxiv2024

The dynamics of Staphylococcal infection and their treatment with antibiotics and bacteriophage in the Galleria mellonella model system

Critical to our understanding of infections and their treatment is the role the innate immune system plays in controlling bacterial pathogens. Nevertheless, many in vivo systems are made or modified such that they do not have an innate immune response. Use of these systems denies the opportunity to examine the synergy between the immune system and antimicrobial agents. In this study we demonstrate that the larva of Galleria mellonella is an effective in vivo model for the study of the population and evolutionary biology of bacterial infections and their treatment. To do this we test three hypotheses concerning the role of the innate immune system during infection. We show: i) sufficiently high densities of bacteria are capable of saturating the innate immune system, ii) bacteriostatic drugs and bacteriophages are as effective as bactericidal antibiotics in preventing mortality and controlling bacterial densities, and iii) minority populations of bacteria resistant to a treating antibiotic will not ascend. Using a highly virulent strain of Staphylococcus aureus and a mathematical computer-simulation model, we further explore how the dynamics of the infection within the short term determine the ultimate infection outcome. We find that immune activation in response to high densities of bacteria leads to a strong but short-lived immune response which ultimately results in a high degree of mortality. Overall, our findings illustrate the utility of the G. mellonella model system in conjunction with established in vivo models in studying infectious disease progression and treatment. Significance statementCentral to our understanding of the course of bacterial infections and their treatment is the contribution of the innate immune system. We use the larvae of Galleria mellonella to test hypothesis about the role of the innate immune system on Staphylococcus aureus infections. We demonstrate that the innate immune system of these larvae can control the infection and be saturated by high bacterial densities. As a consequence of this innate immune system, bacteriostatic drugs and phages are as effective as bactericidal drugs, and minority populations of bacteria resistant to antibiotics do not ascend. Our findings illustrate the utility of G. mellonella as a model for studying infections dynamics and therapeutic strategies.

microbiology↗

bioRxiv2023

Enteric Populations of Escherichia coli are Likely to be Resistant to Phages Due to O Antigen Production

Metagenomic data provide evidence that bacteriophage (phage) abound in the enteric microbiomes of humans. However, the contribution of these viruses in shaping the bacterial composition of the gut microbiome and how these phages are maintained remains unclear. We performed experiments with 751 combinations of 54 Escherichia coli and 9 phage isolates from four fecal microbiota transplantation (FMT) doses and 5 laboratory phages as samples of non-dysbiotic human enteric microbiota. We also developed a mathematical model of the population and evolutionary dynamics of bacteria and phage. Our experiments predict that as a consequence of the production of the O-antigen, most of the E. coli in the human enteric microbiome will be resistant to infections with the array of co-occurring phages. Our modeling suggests that phages are maintained in these enteric communities due to the high rates of transition between the resistant and sensitive states resulting from O-antigen production or spontaneous O-antigen loss, respectively. Based on our observations and predictions from this theory, we postulate that the phage found in the human gut are likely to play little role shaping the strain composition of E. coli of healthy individuals. Although we only investigated E. coli, the mechanism of resistance described here is shared among most of the Gram-negative bacteria. Extended AbstractEvidence is provided that as a consequence of O-antigen-mediated resistance, the genetically diverse array of bacteriophage in the gut microbiome of humans play little or no role in determining the densities and distribution of genetically diverse strain E. coli in this habitat. Our mathematical model predicts, and our experiments support the hypothesis that the phage present in the gut microbiome are maintained by replication on the minority of sensitive bacteria generated by the leakiness of O-antigen-mediated resistance.

microbiology↗

bioRxiv2023

The contribution of abortive infection to preventing populations of Lactococcus lactis from succumbing to infections with bacteriophage

In the dairy industry bacteriophage (phage) contamination significantly impairs the production and quality of products like yogurt and cheese. To combat this issue, the strains of bacteria used as starter cultures possess mechanisms that make them resistant to phage infection, such as envelope resistance, or processes that render them immune to phage infection, such as restriction-modification and CRISPR-Cas. Lactococcus lactis, used to manufacture cheese and other dairy products, can also block the reproduction of infecting phages by abortive infection (Abi), a process in which phage-infected cells die before the phage replicate. We employ mathematical-computer simulation models and experiments with two Lactococcus lactis strains and two lytic phages to investigate the conditions under which Abi can limit the proliferation of phages in L. lactis populations and prevent the extinction of their populations by these viruses. According to our model, if Abi is almost perfect and there are no other populations of bacteria capable of supporting the replication of the L. lactis phages, Abi can protect bacterial populations from succumbing to infections with these viruses. This prediction is supported by the results of our experiment, which indicate that Abi can help protect L. lactis populations from extinction by lytic phage infections. However, our results also predict abortive infection is only one element of L. lactis defenses against phage infection. Mutant phages that can circumvent the Abi systems of these bacteria emerge. The survival of L. lactis populations then depends on the evolution of envelope mutants that are resistant to the evolved host-range phage.

microbiology↗

bioRxiv2017

Plasmodium falciparum dipeptidyl aminopeptidase 3 activity is important for efficient erythrocyte invasion.

Parasite egress from infected erythrocytes and invasion of new erythrocytes are essential for the exponential asexual replication of the malaria parasite, and both processes are regulated and mediated by proteases. The putative cysteine protease dipeptidyl aminopeptidase 3 (DPAP3) was previously suggested to be essential for parasite egress, but little is known about its biological function. Here, we demonstrate that DPAP3 has proteolytic activity, but contrary to previously studied DPAPs, removal of its prodomain is not required for activation. Interestingly, P. falciparum DPAP3 localizes to merozoite apical organelles from which it is secreted immediately before egress. Using a conditional knock out approach coupled to complementation studies with wild type or mutant DPAP3, we show that DPAP3 activity is critical for efficient RBC invasion and overall parasite replication, and demonstrate that it does not play a role in parasite egress. Overall, this study establishes DPAP3 as a key regulator of erythrocyte invasion.

microbiology↗