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Ronald M. Weiner
Professor Emeritus
Ph.D., Iowa State University, 1970
Fax: (301) 314-9489
E-mail:
rweiner@umd.edu
Research Interests:
There is an ongoing and active research program centered about two
areas, marine biofilms and complex carbohydrate degradation in the
mare environment.
We are learning how prokaryotes adhere to, and colonize, marine
surfaces. We are focusing on capsular exopolysaccharide (EPS) which
may be a primary adhesion and which is a dominant component of marine
biofilms. We most commonly study a paradigm, marine genus which
we named Hyphomonas and which has species isolated from deep-sea
hydrothermal vents. It's species have biphasic life cycles with
a pelagic and adherent stage. This complex prokaryotic life cycle
and its evolution and taxonomy have been elucidated by my laboratory.
These bacteria tolerate a strikingly wide range of environmental
conditions and have both autotrophic and heterotrophic capability.
We are examining the molecular mechanisms and developmental cell
biology that confer a potent survival advantage upon this taxon.
We are using these mechanisms and biofilm probes that we have developed
to screen for biofilm forming pathogens in the environment and on
contaminated food products, in collaboration with Dr. S Joseph.
As part of complex biofilms, we have investigated the way that periphytic
bacteria signal invertebrates to colonize surfaces. We have shown
that some Shewanella and Hyphomonas species synthesize enzymes involved
in tyrosine degradation and oxidation and that a primary product,
L-dihydroxyphenyl alanine (L-Dopa), can cue invertebrate set and
enhance the integrity of biofilms. We have cloned the parahydroxy-phenyl-pyruvate
oxidase (PHPPO) operon and isolated its product, homogentisic acid.
The function and expression of PHPPO among diverse marine species
has been determined.
We are also studying enzymes that degrade relatively insoluble complex
polysaccharides (CP) that are important in marine biofilms and marine
plant and animal symbioses. These include cellulases, chitinases,
agarases and alginases. We are learning about their expression,
mode of action and role in inanimate surface or algal colonization.
The laboratory is focusing on cell biological adaptations that optimize
enzyme function. Briefly we have discovered that the marine bacterium,
strain 2-40 (we proposed to name it to the genus, Microbulbifer),
synthesizes complex structures that house, organize, and protect
consortia of hydrolytic enzymes that bring to bear a concerted attack
on the CP.
This is very important because in terrestrial habitats, a specialized
group of microorganisms degrade a significant portion of the more
than 52 billion tons of cellulose that accumulate yearly by producing
structures termed cellulosomes. These structures bind and organize
the cellulolytic enzymes for a concerted attack on the CP, making
the degradative process much more efficient. In the oceans, on the
other hand, much less is known about how the annual production of
the more than 25 billion tons of ICP, found in biofilms, associated
with algae, and in invertebrate shells, is recycled to usable carbon.
It turns out that 2-40 belongs to a recently discovered group of
bacteria that includes degradative species such as shipworm symbionts,
that recycle complex carbohydrates. 2-40, was isolated from decaying
marine grass, Spartina, and appeared capable of single-handedly
decomposing the plant. It was found to synthesize a battery of proteases,
lipases, and at least 10 different enzyme systems that attack complex
carbohydrates, including agarases, chitinases, alginases, pullulanases
and laminarinases. The enzymes were best induced by the homologous
substrate and their synthesis was repressed by glucose.
Marine bacterium 2-40 was found, by scanning and transmission electron
microscopy, to produce surface protuberances (termed hydrolysomes),
when growing on complex carbohydrates but not when growing on simple
sugars. Structurally the hydrolysomes resembled cellulosomes.The
isolated hydrolysomes have potential applications in the bioremediation
of biofouled surfaces, aquaculture wastes (e.g. shrimp and crab-shell)
and plants efficiently recycling these to usable feedstock. They
have medical applications as well.
In collaboration with DOE, we sequenced the genome of 2-40. In collaboration
with Dr. S. Hutcheson we have initiated a genome wide functional
genomics and proteomics study. At least 150 open reading frames
coding for CP depolymerases have been identified thus far. Of these,
22 have been identified as likely cellulases, cellobiases, or cellodextrinases
and at least 7 identified as xylanases. Additionally, there are
as many as 15 likely pectin lyases in the draft sequence.
The completed draft sequence of the 2-40 genome enabled the first
genome-wide analysis of a microbial chitinolytic system. The chitinase
system of 2-40 was found to include secreted chitin depolymerases
(ChiA, ChiB, ChiC), a secreted chitin binding protein (CbpA), periplasmic
chitooligosaccharide modifying enzymes, putative sugar transporters,
and a cluster of genes encoding cytoplasmic proteins involved in
GlcNAc metabolism. Each chitin depolymerase was detectable in culture
supernatants of chitin grown 2-40 and was active against chitin
and glycol chitin.
The agarase system was also examined to elucidate the constituent
enzymes and functional domains. Several strategies, including genome
analysis, revealed five enzymes apparently involved in the degradation
of agar: AgaA, AgaB, AgaC, AgaD, AgaE. These all shared at least
40% similarity to a known agarase. The genes for these agarases
were found dispersed within the 2-40 genome. Zymograms and thin
layer chromatography of cloned AgaB and AgaF revealed that they
are beta-agarases. The major product of AgaB activity is neoagarotretraose,
indicating that it is a beta-agarase I.
To our knowledge, M. degradans 2-40 is the first marine bacterium
shown to have a complete enzymatic system capable of completely
degrading all three of the major components of plant cell walls.
Based upon the number of its degradative enzyme systems, 2-40 appears
to be a versatile saprophyte and a significant participant in the
marine carbon cycle.
Reviewed Publications 2004 - present
Weiner, R. 2004. The
Hyphomonas.
in: Bergey's
Manual of Determinative Bacteriology. 10th ed.,
Vol 3, Williams and Wilkins
Howard M, N
Ekborg, L Taylor, S Hutcheson and R Weiner.
2004. Genome-wide identification and analysis
polyserine linker domains in prokaryotes with emphasis on the
marine bacterium, Microbulbifer
degradans. J Protein Sci 13:
1422 –1425.
Howard M, N
Ekborg, L Taylor, R Weiner and S Hutcheson.
2004. Chitinase B of Microbulbifer
degradans strain 2-40 contains two catalytic domains with
different chitinolytic activities. J
Bacteriol 186: 1297-1303.
de
Renzende, C, L Carr, S Joseph and R
Weiner. 2005. A capsular polysaccharide surrounds smooth and
rugose types of Salmonella.
enterica serovar
Typhimurium DT104
Appl Env
Microbiol. 71:7345-7351.
Ekborg, N, JM
Gonzalez M Howard, L Taylor, S Hutcheson and RM Weiner.
2005. Saccharophagus degradans gen. nov.,
sp. nov., A versatile marine bacterial
degrader of complex polysaccharides. Int
J Syst Evolut
Microbiol 55: 1545-1549.
Ekborg, N,
Larry E. Taylor, A Longmire, B
Henrissat, R Weiner and S Hutchison.
2006.
Genomic and proteomic analysis of the
agarolytic system encoded by Saccharophagus degradans
2-40. Appl Env
Microbiol 72:3396-33405.
Badger,
JH, T. R. Hoover, YV Brun, RM Weiner, MT
Laub, G Alexandre,
J Mrázek, Q Ren,
IT Paulsen, KE Nelson, HM Khouri,
D Radune, J
Sosa, RJ Dodson, SA Sullivan, MJ Rosovitz,
R Madupu, LM
Brinkac, AS Durkin, SC Daugherty, SP
Kothari, MG Giglio, L Zhou, D H.
Haft, JD Selengut, TM
Davidsen, Q Yang, N
Zafar, and NL Ward. 2006. Comparative genomic evidence for a
close relationship between the dimorphic
prosthecate bacteria Hyphomonas
neptunium and Caulobacter
crescentus. J.
Bacteriol.
188: 6841- 6850.
J
Henshaw, A Horne-Bitschy,
Al LAmmerts van
Bueren, V Money, D Bolam, M
Czjzek, N. Ekborg,
RWeiner, S Hutcheson, G Davies, A Boraston
and HGilbert. 2006. Family 6
Carbohydrate Binding Modules in β-Agarases Display Exquisite
Selectivity for the Non-Reducing Termini of
Agarose chains. JBC. 281:17099-17107
Taylor l, B
Henrissat,
P
Coutinho,
N. Ekborg,
S.Hutcheson,
and R Weiner.
2006. A complete cellulase
system in the marine
bacterium Saccharophagus
degradans
strain 2-40T.
J
Bacteriol.
188:3849-3861.
Weiner
R , L Taylor II, B Henrissat, L
Hauser, M Land, P Coutinho,
CRancurel, E Saunders, A Longmire, H
Zhang, E Bayer, H Gilbert, F Larimer, I Zhulin,
N. Ekborg, R Lamed, P Richardson, I Borovok, and S Hutcheson, 2008
Complete Genome Sequence of the Complex Carbohydrate-Degrading
Marine Bacterium, Saccharophagus degradans strain 2-40T
PLoS Genetics.
http://www.plosgenetics.org/doi/pgen.1000087. | |