RODMRP - resilient on demand multicast routing protocol

ODMRP (On-Demand Multicast Routing Protocol) [6] [8] [2] is a popular multicast protocol for wireless ad hoc networks. The strengths of ODMRP are simplicity, high packet delivery ratio, and non-dependency on a specific unicast protocol. ODMRP floods a route request over the entire network to select a set of forwarding nodes for packet delivery. However, a single forwarding path is vulnerable to node failures, which are common due to the dynamic nature of mobile ad hoc networks. Furthermore, a set of misbehaving or malicious nodes can create network partitions and mount Denial-of-Service (DoS) attacks. This thesis proposes a ODMRP-based wireless multicast protocol named RODMRP that offers more reliable forwarding paths in face of node and network failures. A subset of the nodes that are not on forwarding paths rebroadcast received packets to nodes in their neighborhoods to overcome perceived node failures. This rebroadcasting creates redundant forwarding paths to circumvent failed areas in the network. Each node makes this forwarding decision probabilistically. Our simulation results indicate that RODMRP improves packet delivery ratio with minimal overheads, while retaining the original strengths of ODMRP

Resilient-ODMRP: Resilient On-Demand Multicast Routing Protocol

(On-Demand Multicast Routing Protocol) [5] [7] [1] is a popular multicast protocol for wireless ad hoc networks. The strengths of ODMRP are simplicity, high packet delivery ratio, and non-dependency on a specific unicast protocol. ODMRP floods a route request over the entire network to select a set of forwarding nodes for packet delivery. However, a single forwarding path is vulnerable to node failures, which are common due to the dynamic nature of mobile ad hoc networks. Furthermore, a set of misbehaving or malicious nodes can create network partitions and mount Denial-of-Service (DoS) attacks. We propose a ODMRP-based wireless multicast protocol named Resilient-ODMRP that offers more reliable forwarding paths in face of node and network failures. A subset of the nodes that are not on forwarding paths rebroadcast received packets to nodes in their neighborhoods to overcome perceived node failures. This rebroadcasting creates redundant forwarding paths to circumvent failed areas in the network. Each node makes this forwarding decision probabilistically. Our simulation results indicate that Resilient-ODMRP improves packet delivery ratio with minimal overheads, while retaining the original strengths of ODMRP

\u3ci\u3eCandida albicans ISW2 Regulates\u3c/i\u3e Chlamydospore Suspensor Cell Formation and Virulence \u3ci\u3eIn Vivo\u3c/i\u3e in a Mouse Model of Disseminated Candidiasis

Formation of chlamydospores by Candida albicans was an established medical diagnostic test to confirm candidiasis before the molecular era. However, the functional role and pathological relevance of this in vitro morphological transition to pathogenesis in vivo remain unclear. We compared the physical properties of in vitro-induced chlamydospores with those of large C. albicans cells purified by density gradient centrifugation from Candida infected mouse kidneys. The morphological and physical properties of these cells in kidneys of mice infected intravenously with wild type C. albicans confirmed that chlamydospores can form in infected kidneys. A previously reported chlamydospore-null Δisw2/ Δisw2 mutant was used to investigate its role in virulence and chlamydospore induction. Virulence of the Δisw2/Δisw2 mutant strain was reduced 3.4-fold compared to wild type C. albicans or the ISW2 reconstituted strain. Altered host inflammatory reactions to the null mutant further indicate that ISW2 is a virulence factor in C. albicans. ISW2 deletion abolished chlamydospore formation within infected mouse kidneys, whereas the reconstituted strain restored chlamydospore formation in kidneys. Under chlamydospore inducing conditions in vitro, deletion of ISW2 significantly delayed chlamydospore formation, and those late induced chlamydospores lacked associated suspensor cells while attaching laterally to hyphae via novel spore-hypha septa. Our findings establish the induction of chlamydospores by C. albicans during mouse kidney colonization. Our results indicate that ISW2 is not strictly required for chlamydospores formation but is necessary for suspensor cell formation. The importance of ISW2 in chlamydospore morphogenesis and virulence may lead to additional insights into morphological differentiation and pathogenesis of C. albicans in the host microenvironment

\u3ci\u3eCandida albicans ISW2 Regulates\u3c/i\u3e Chlamydospore Suspensor Cell Formation and Virulence \u3ci\u3eIn Vivo\u3c/i\u3e in a Mouse Model of Disseminated Candidiasis

Formation of chlamydospores by Candida albicans was an established medical diagnostic test to confirm candidiasis before the molecular era. However, the functional role and pathological relevance of this in vitro morphological transition to pathogenesis in vivo remain unclear. We compared the physical properties of in vitro-induced chlamydospores with those of large C. albicans cells purified by density gradient centrifugation from Candida infected mouse kidneys. The morphological and physical properties of these cells in kidneys of mice infected intravenously with wild type C. albicans confirmed that chlamydospores can form in infected kidneys. A previously reported chlamydospore-null Δisw2/ Δisw2 mutant was used to investigate its role in virulence and chlamydospore induction. Virulence of the Δisw2/Δisw2 mutant strain was reduced 3.4-fold compared to wild type C. albicans or the ISW2 reconstituted strain. Altered host inflammatory reactions to the null mutant further indicate that ISW2 is a virulence factor in C. albicans. ISW2 deletion abolished chlamydospore formation within infected mouse kidneys, whereas the reconstituted strain restored chlamydospore formation in kidneys. Under chlamydospore inducing conditions in vitro, deletion of ISW2 significantly delayed chlamydospore formation, and those late induced chlamydospores lacked associated suspensor cells while attaching laterally to hyphae via novel spore-hypha septa. Our findings establish the induction of chlamydospores by C. albicans during mouse kidney colonization. Our results indicate that ISW2 is not strictly required for chlamydospores formation but is necessary for suspensor cell formation. The importance of ISW2 in chlamydospore morphogenesis and virulence may lead to additional insights into morphological differentiation and pathogenesis of C. albicans in the host microenvironment

Isw2p expression induces chlamydospore formation in kidneys of mice with disseminated candidiasis.

<p>Representative GMS stains of kidney sections dissected from mice infected with WT, and reconstituted DRL7 strains. Arrowheads indicate representative chlamydospores in histological sections of infected mouse kidneys at 3–6 days PI. Large arrow in left-lower corner image indicates a solitary chlamydospore in a resolving lesion in mouse kidney cortex at 8 days PI. Scale bar, 100 μm.</p

DRL6 induces chlamydospores in Staib agar.

<p><b>(A)</b> Abundant chlamydospore formation by <i>C</i>. <i>dubliniensis</i> Wü284. <b>(B)</b> Poor filamentation and no detectable chlamydospores by <i>C</i>. <i>albicans</i> SC5314. <b>(C)</b> Occasionally visible chlamydospore formation by DRL6 (<i>Δisw2/Δisw2</i>) strain in Staib agar as indicated by the black arrow heads. Plates were grown at room temperature in the dark for up to 7 days, and representative pictures are from at least 3 independent experiments.</p

Chlamydospore-like structures are observed in <i>C</i>. <i>albicans</i>-infected mouse kidneys at day 3 post-inoculation.

<p>Top panel: A representative section from infected kidney cortex stained using GMS three days PI with <i>C</i>. <i>albicans</i>. Chlamydospore-like structures are indicated by the arrows. Middle panel: Periphery of a resolving <i>Candida</i>-infected lesion shows isolated chlamydospore-like structures (arrows). Bottom panel: Higher magnification of the same histopathology sections shows spherical fungal spores with a diameter of 8 μm.</p

Isw2p expression induces chlamydospore formation in kidneys of mice with disseminated candidiasis.

<p>Representative GMS stains of kidney sections dissected from mice infected with WT, and reconstituted DRL7 strains. Arrowheads indicate representative chlamydospores in histological sections of infected mouse kidneys at 3–6 days PI. Large arrow in left-lower corner image indicates a solitary chlamydospore in a resolving lesion in mouse kidney cortex at 8 days PI. Scale bar, 100 μm.</p

Late induction of chlamydospores lacking suspensor cells in <i>Δisw2/Δisw2</i> mutant strain compared to its parent strain.

<p><b>(A)</b> Time course of chlamydospore development over six weeks to verify a developmental pattern of chlamydospores lacking suspensor cells in DRL6 (<i>Δisw2/Δisw2)</i> strain. Images captured at 2 and 4 weeks are shown. The WT SC5314 and <i>ISW2</i> complemented DRL7 strains initiated chlamydospore formation within 5 to 10 days on corn meal agar supplemented with 1% Tween 80. In contrast, the DRL6 (<i>Δisw2/Δisw2</i>) strain had no visible chlamydospores by day 14 but did produce lateral chlamydospores without suspensor cells after 4 to 5 weeks of incubation. <b>(B)</b> Micrographs of Calcofluor White-stained chlamydospores from <i>C</i>. <i>albicans</i> SC5314 (A1, A2) and the DRL6 (<i>Δisw2/Δisw2</i>) strain (B1, B2) captured after 2 and 4 weeks of incubation, respectively, with an Olympus FV500 Inverted (Olympus IX-81) Confocal Microscope. The average size of the WT chlamydospores formed on suspensor cells are 8.32 ± 0.94 (SD) μm, whereas the chlamydospores lacking suspensor cells are 7.88 ± 1.12 (SD) μm; n = 50. The images were analyzed with ImageJ (NIH) software for diameter measurement.</p