ORIGINAL PAPER
Tomi Lahtinen Æ Mirva Kosonen Æ Marja Tiirola
Matti Vuento Æ Christian Oker-Blom
Diversity of bacteria contaminating paper machines
Received: 23 August 2005 / Accepted: 6 February 2006 / Published online: 7 March 2006
Ó Society for Industrial Microbiology 2006
Abstract Formation of microbial biofilms and slimes is
a general and serious problem in the operation of
paper machines. Studies of microbial populations in
paper machine-derived biofilms have been conducted
using standard microbiological procedures; however,
the bacterial genera present in this type of samples as
well as their diversity are quite poorly known. Here,
the bacterial diversity of 38 process water and 22
biofilm samples from four different Finnish paper
machines were analyzed by length heterogeneity anal-
ysis of PCR-amplified 16S ribosomal DNA (LH-PCR).
In addition, sequencing of the amplified 16S rRNA
gene from 69 clones was conducted for characteriza-
tion of the bacterial genera present in biofilm and
slime samples. The LH-PCR profiles of both the free-
living (process waters) and immobilized (biofilms)
bacteria were diverse at all stages of the papermaking
process. Out of the 69 sequenced clones, 44 belonged
to alpha-Proteobacteria, most of which were close to
the nitrogen-fixing root nodule genera Sinorhizobium,
Rhizobium and Azorhizobium. Other clones were as-
signed to beta- and gamma-Proteobacteria and the
phylum Bacteroidetes. In addition, eight of the clones
were assigned to a yet uncultivated phylum, TM7.
Finally, epifluorescence microscopy revealed that
Gram-negative bacteria were predominant in both the
biofilm (65%) and process water (54%) samples and a
small coccoid cell morphology was most common in
all samples. Together, our results show that the
analysis of microbial samples from paper machines
using modern molecular biology techniques adds
valuable information and should, therefore, be useful
as a more specific and sensitive microbiological
method for the paper industry. This information could
further be applied, e.g., in the development of more
specific and environmental friendly antimicrobial
agents for paper mills.
Keywords Biofilm Æ Slime Æ Pulp Æ Paper machine Æ
16S rRNA Æ LH-PCR Æ Rhizobia
Introduction
Growth of microorganisms in paper machines and
board mills may cause severe economical losses as a
consequence of reduced production rates. This is due to
the increased number of web breaks and more frequent
down time for the cleaning and maintenance of the
machinery. Microbial contaminations also cause higher
production costs due to larger consumption of additives
and biocides, reduction in the lifetime of the equipment
as well as deterioration in the quality of the final prod-
uct. The reuse of white water and recycling of the pulp
are the main reasons for bacterial and fungal contami-
nation [4]. Particularly problematic are those microbial
contaminants that form biofilms and slimes. Therefore,
it is necessary to obtain more detailed information
regarding the bacterial groups forming these biofilms as
well as the mechanisms by which they attach and/or
detach the surfaces in paper machines.
Earlier studies on bacterial communities associated
with paper mills have shown that several aerobic and
anaerobic genera, such as Bacillus, Sphaerotilus, Kle-
bsiella, Achromobacter and Pseudomonas and combina-
tions thereof form typical bacterial microbiota in paper
industry [4]. However, since most studies are based on
physiological and biochemical characterization of the
bacterial isolates, many of the strains may have been
misidentified. By supporting the strain identification
with phylogenetical methods, Vaisanen et al. [17] dis-
covered that the most common bacteria present at the
wet end of the paper machine belonged to the Bacillus,
T. Lahtinen Æ M. Kosonen Æ M. Tiirola Æ M. Vuento
C. Oker-Blom (&)
NanoScience Center,
Department of Biological and Environmental Science,
University of Jyva
¨
skyla
¨
, P.O. Box 35, 40014, Jyva
¨
skyla
¨
,
Finland
E-mail: okerblom@jyu.fi
Tel.: +358-14-2602285
Fax: +358-14-2602221
J Ind Microbiol Biotechnol (2006) 33: 734–740
DOI 10.1007/s10295-006-0105-4