SummaryPseudomonas aeruginosa is an opportunistic pathogen capable of producing a wide variety of virulence factors, including extracellular rhamnolipids and lipopolysaccharide. Rhamnolipids are tenso-active glycolipids containing one (mono-rhamnolipid) or two (di-rhamnolipid) L-rhamnose molecules. Rhamnosyltransferase 1 (RhlAB) catalyses the synthesis of mono-rhamnolipid from dTDP-L-rhamnose and b-hydroxydecanoyl-b-hydroxydecanoate, whereas di-rhamnolipid is produced from mono-rhamnolipid and dTDP-L-rhamnose. We report here the molecular characterization of rhlC, a gene encoding the rhamno-production in P. aeruginosa. RhlC is a protein consisting of 325 amino acids with a molecular mass of 35.9 kDa. It contains consensus motifs that are found in other glycosyltransferases involved in the transfer of L-rhamnose to nascent polymer chains. To verify the biological function of RhlC, a chromosomal mutant, RTII-2, was generated by insertional mutagenesis and allelic replacement. This mutant was unable to produce di-rhamnolipid, whereas mono-rhamnolipid was unaffected. In contrast, a null rhlA mutant (PAO1-rhlA) was incapable of producing both mono-and di-rhamnolipid. Complementation of mutant RTII-2 with plasmid pRTII-26 containing rhlC restored the level of di-rhamnolipid production in the recombinant to a level similar to that of the wild-type strain PAO1. The rhlC gene was located in an operon with an upstream gene (PA1131) of unknown function. A s 54 -type promoter for the PA1131±rhlC operon was identified, and a single transcriptional start site was mapped. Expression of the PA1131±rhlC operon was dependent on the P. aeruginosa rhl quorum-sensing system, and a well-conserved lux box was identified in the promoter region. The genetic regulation of rhlC by RpoN and RhlR was in agreement with the observed increasing RhlC rhamnosyltransferase activity during the stationary phase of growth. This is the first report of a rhamnosyltransferase gene responsible for the biosynthesis of di-rhamnolipid.

L-Rhamnose (L-Rha) is a component of the lipopolysaccharide (LPS) core, several O antigen polysaccharides, and the cell surface surfactant rhamnolipid of Pseudomonas aeruginosa. In this study, four contiguous genes (rmlBDAC) responsible for the synthesis of dTDP-L-Rha in P. aeruginosa have been cloned and characterized. Non-polar chromosomal rmlC mutants were generated in P. aeruginosa strains PAO1 (serotype O5) and PAK (serotype O6) and LPS extracted from the mutants was analysed by SDS-PAGE and Western immunoblotting. rmlC mutants of both serotype O5 and serotype O6 synthesized a truncated core region which was unable to act as an attachment point for either A-band or B-band O antigen. A rmd rmlC PAO1 double mutant (deficient in biosynthesis of both D-Rha and L-Rha) was constructed to facilitate structural analysis of the mutant core region. This strain has an incomplete core oligosaccharide region and does not produce A-band O antigen. These results provide the genetic and structural evidence that L-Rha is the receptor on the P. aeruginosa LPS core for the attachment of O polysaccharides. This is the first report of a genetically defined mutation that affects the synthesis of a single sugar in the core oligosaccharide region of P. aeruginosa LPS, and provides further insight into the mechanisms of LPS biosynthesis and assembly in this bacterium.

Glucose-1-phosphate thymidylyltransferase (RmlA; E.C. 2.7.7.24) is the ®rst of four enzymes involved in the biosynthesis of dTDP-lrhamnose, the precursor of l-rhamnose, a key component of the cell wall of many pathogenic bacteria. RmlA catalyses the condensation of thymidine triphosphate (dTTP) and -d-glucose-1-phosphate (G1P), yielding dTDP-d-glucose. RmlA from Pseudomonas aeruginosa has been overexpressed and puri®ed. Crystals of the enzyme have been grown using the sitting-drop vapour-diffusion technique with PEG 6000 and lithium sulfate as precipitant. Several diffraction data sets of single frozen crystals were collected to a resolution of 1.66 A Ê . Crystals belonged to space group P1, with unit-cell parameters a = 71.5, b = 73.1, c = 134.7 A Ê , = 89.9, = 80.9, = 81.1 . The asymmetric unit contains eight monomers in the form of two RmlA tetramers with a solvent content of 51%. Selenomethionine-labelled protein has been obtained and crystallized.

<p class="NoParagraphStyle" align="center"><strong>ABSTRACT</strong></p><p class="NoParagraphStyle">This research aimed to obtain the performance of super intensive white shrimp rearing using zero water discharge (ZWD) system. This study consisted of four steps, (1) activation and cultivation of nitrifying bacteria, microalgae <em>C. calcitrans</em> and <em>B. megaterium</em>; (2) acclimatization of Pacific white shrimp PL10 with 30 g/L of salinity and decreasing salinity at 2–3 g/L/day; (3) conditioning of ZWD system; (4) white shrimp rearing in 400 L of tank for ten weeks. The experiment used three treatments, (a) shrimp reared without any addition of microbial agent with water exchange conducted every week as much as10–20% of total rearing volume as control (K); (b) ZWD systems with the applications of nitrifying bacteria, (<em>C. calcitrans</em> and <em>B. megaterium</em>) without water discharge  (P1); and (c) ZWD system with the application of microalgae <em>C. calcitrans</em> and <em>B. megaterum</em> without water discharge (P2). According to the results, application of nitrifying bacteria, microalgae <em>C. calcitrans</em> and <em>B. megaterium</em> were able to improve the performance of ZWD system performance of white shrimp rearing at low salinity. In addition, the ZWD system was also able to increase the growth rate and survival rate of shrimp when it compared to control. The best rearing performance was found in ZWD system with application of microalgae <em>C. calcitrans</em> and <em>B. megaterium</em>.</p><p class="NoParagraphStyle"> </p><p class="NoParagraphStyle">Keywords: <em>Litopenaeus vannamei</em>, ZWD, low salinity, microalgae, nitrification bacteria.</p><p class="NoParagraphStyle"> </p><p class="NoParagraphStyle"> </p><p class="NoParagraphStyle"> </p><p class="NoParagraphStyle" align="center"><strong>ABSTRAK</strong></p><p class="NoParagraphStyle">Penelitian ini bertujuan untuk mengetahui kinerja budidaya udang putih super intensif bersalinitas rendah menggunakan sistem <em>zero water discharge</em> (ZWD).  Penelitian ini terbagi dalam tiga, yaitu (1) aktivasi dan kultur bakteri nitrifikasi, mikroalga <em>C. calcitrans</em> dan <em>B. megaterium</em>; (2) aklimatisasi udang putih PL10 salinitas 30 g/L dan penurunan salinitas 2–3 g/L/hari; (3) pengondisian dari sistem ZWD; (4) pemeliharaan udang putih selama 10 minggu di bak bervolume 400 L. Penelitian ini menggunakan tiga perlakuan ; (a) perlakuan kontrol tanpa penambahan  mikroba dan pergantian air setiap minggu sebanyak 10–20% (K) ; (b) sistem ZWD dengan bakteri nitrifikasi, mikroalga <em>C. calcitrans</em> dan <em>B. megaterium</em> tanpa pergantian air (P1); (c) sistem ZWD dengan  mikroalga <em>C. calcitrans </em>dan <em>B. megaterum </em>tanpa pergantian air (P2). Berdasarkan hasil yang didapat, aplikasi bakteri nitrifikasi, mikroalga C<em>. calcitrans</em> dan <em>B. megaterum</em> mampu meningkatkan kineja sistem ZWD pada budidaya udang putih <em>L. vannamei </em>bersalinitas rendah. Selain itu, aplikasi bakteri nitrifikasi, mikroalga <em>C. calcitrans</em> dan <em>B. megaterum </em>pada sistem ZWD juga mampu meningkatkan laju pertumbuhan dan sintasan udang putih dibanding dengan kontrol. Kinerja pemeliharaan terbaik dijumpai pada sistem ZWD dengan aplikasi mikroalga <em>C. calcitrans</em> dan <em>B. megaterum</em>.</p><p class="NoParagraphStyle"> </p><p class="NoParagraphStyle">Kata kunci: bakteri nitrifikasi, <em>Litopenaeus vannamei</em>, mikroalga, salinitas rendah, ZWD </p>

Lecturers are one of the essential components in an education system in higher education. The roles, tasks and responsibilities of lecturers are very meaningful in realizing the goals of national education, which are to educate the life of the nation, improve the quality of Indonesian people, cover faith and piety, noble character, and mastery of science, technology, and adaptation. Therefore it is necessary to pay great attention to matters relating to improving the performance of lecturers so that lecturers can carry out their tasks more professionally. This study aims to analyze the factors that influence the performance of Permanent Lecturers at Buton Muhammadiyah University. These factors are motivation, competency, leadership, and work environment. The subjects in this study were Permanent Lecturers at the University of Muhammadiyah Buton. The study was conducted using a questionnaire as an primary data collection instrument. Samples taken as many as 40 lecturers using the convinience samling method. To measure the factors that influence the performance of Permanent Lecturers at Buton Muhammadiyah University, multiple analysis is used. The results showed that the motivation, leadership competency, and the work environment of the lecturer had a positive influence on the performance of the Permanent Lecturer at Buton Muhammadiyah University.