Saudi Cultural Missions Theses & Dissertations
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Item Restricted Viruses of Coagulase-Negative Staphylococcus: understanding viral diversity, defence systems, and host range dynamics in the skin microbiome(Saudi Digital Library, 2029) Alsaadi, Samah Eid; Horsburgh, MalHuman skin is colonised by Staphylococcus species that have varying abundance across different body regions, with coagulase-negative staphylococcal (CoNS) species accounting for a significant proportion of the skin microbiome. Previous studies demonstrated the relative abundance of Staphylococcus species differs across skin sites and that the skin virome influences the dynamics of bacterial populations of the skin. Bacteriophages (phages) are widely present in human skin and modulate its bacterial populations, including CoNS species. This study aimed to investigate the diversity of cutaneous phages that infect major skin CoNS species, such as S. hominis, S. epidermidis, and S. capitis. Skin swabs were collected from 80 healthy volunteers at four body sites to isolate phages and tested their infection of Staphylococcus species. A total of 40 phages were isolated and genome sequenced, corresponding to six genetic clusters, with two clusters representing novel phages. Phage infection was qualitatively assessed using a wide host range of 140 strains across eight Staphylococcus species. The novel phage, named øAlsa, exhibited a greater ability to infect S. hominis, which was broadly resistant to most identified phages when compared to other CoNS species, suggesting the presence of a defence barrier that limited phage infection. Genomic analysis revealed the widespread presence of bacterial defence systems, including restriction-modification (R-M) systems, abortive infection (Abi) systems, as well as variable prophage content among species. Notably, Type IV R-M was widely present in S. hominis, which could indicate species-specific resistance that contributes to the observed phage infectivity profile. However, no definitive links between phage susceptibility and defence diversity could be determined. Biofilm formation was assessed in representative strains of S. hominis, S. epidermidis, and S. capitis, exhibiting strong biofilm formation in both phage-resistant and phage-susceptible strains, with no clear correlation between biofilm formation and phage resistance. However, Alsa phages, specifically øAlsa_2, reduced biofilm biomass, suggesting phage-associated activities that could influence receptor accessibility. Together, these findings highlight the intricate relationships between staphylococcal phages, bacterial defence systems, receptor accessibility, and biofilm formation, which collectively contribute to the populations of CoNS and their phages on human skin.9 0Item Restricted Viruses of Coagulase-Negative Staphylococcus: understanding viral diversity, defence systems, and host range dynamics in the skin microbiome(Saudi Digital Library, 2025) Alsaadi, Samah Eid; Horsburgh, MalHuman skin is colonised by Staphylococcus species that have varying abundance across different body regions, with coagulase-negative staphylococcal (CoNS) species accounting for a significant proportion of the skin microbiome. Previous studies demonstrated the relative abundance of Staphylococcus species differs across skin sites and that the skin virome influences the dynamics of bacterial populations of the skin. Bacteriophages (phages) are widely present in human skin and modulate its bacterial populations, including CoNS species. This study aimed to investigate the diversity of cutaneous phages that infect major skin CoNS species, such as S. hominis, S. epidermidis, and S. capitis. Skin swabs were collected from 80 healthy volunteers at four body sites to isolate phages and tested their infection of Staphylococcus species. A total of 40 phages were isolated and genome sequenced, corresponding to six genetic clusters, with two clusters representing novel phages. Phage infection was qualitatively assessed using a wide host range of 140 strains across eight Staphylococcus species. The novel phage, named øAlsa, exhibited a greater ability to infect S. hominis, which was broadly resistant to most identified phages when compared to other CoNS species, suggesting the presence of a defence barrier that limited phage infection. Genomic analysis revealed the widespread presence of bacterial defence systems, including restriction-modification (R-M) systems, abortive infection (Abi) systems, as well as variable prophage content among species. Notably, Type IV R-M was widely present in S. hominis, which could indicate species-specific resistance that contributes to the observed phage infectivity profile. However, no definitive links between phage susceptibility and defence diversity could be determined. Biofilm formation was assessed in representative strains of S. hominis, S. epidermidis, and S. capitis, exhibiting strong biofilm formation in both phage-resistant and phage-susceptible strains, with no clear correlation between biofilm formation and phage resistance. However, Alsa phages, specifically øAlsa_2, reduced biofilm biomass, suggesting phage-associated activities that could influence receptor accessibility. Together, these findings highlight the intricate relationships between staphylococcal phages, bacterial defence systems, receptor accessibility, and biofilm formation, which collectively contribute to the populations of CoNS and their phages on human skin.9 0