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Abstract
The review covers investigations on wood-inhabiting bacteria and their significance in wood quality carried out in the Hamburg institute, with some additional literature. It addresses bacteria isolated from various woody tissues, their action on pits and woody cell walls, examples for wood discolouration by bacteria, the degradation of wood in soil and water environments and of timber treated with preservatives, methods for decay measurement, the efficacy of preservatives, trends to detoxify treated timber waste and aspects of bacteria as bioprotectants.
... While fungi play a dominant role in the decomposition of wood above ground or in soil contact, bacterial decomposition becomes more relevant under environmental conditions, where fungal activity (except soft rot fungi) is suppressed due to limited oxygen availability, such as buried wood or submerged under water (e.g. Björdal et al. 1999;Holt and Jones 1983;Kim et al. 1996;Schmidt and Liese 1994). But there is also another adverse impact of bacteria on timber wood, which relates to the capacity to degradation wood preservatives (e.g. ...
... Daniel and Nilsson 1985;Greaves 1968;Singh and Wakeling 1997). The resulting detoxification of preservatives can then facilitate a subsequent fungal wood decay (Mai et al. 2004;Schmidt and Liese 1994;Wallace and Dickinson 2006). Although a bacteriostatic effect of the preservatives has been proven in the laboratory, the failure of treated timber in use shows the limitations of such experiments (Greaves 1973;Liese and Schmidt 1975;Edlund and Nilsson 1999). ...
... In the case of metal-containing preservatives, it is hypothesized that the heavy metals could be inactivated by extracellular bacterial slime secretion and formation of a non-toxic complex (Daniel et al. 1987;Greaves 1971). Schmidt and Liese (1994) stated that the reduced efficacy under environmental conditions was caused by acids produced by bacteria which led to a lower pH value, so that fixed preservatives were lost from the wood by leaching. Clausen (2000b) was able to isolate 13 different metal-tolerant bacterial species, including Acinetobacter calcoaceticus, Aureobacterium esteroaromaticum, Klebsiella oxytoca and Bacillus licheniformis. ...
Wood decay fungi and bacteria play a crucial role in natural ecosystems, contributing to the decomposition of lignocellulosic materials and nutrient cycling. However, their activity poses significant challenges in timber durability, impacting industries reliant on wood as a construction material. This review examines the diversity of microorganisms damaging timber used indoors and outdoors. Additionally, traditional and advanced methods for microbial identification are discussed, with a focus on DNA-based, culture-independent sequencing methods whose importance has increased massively in recent years. It also provides an overview of the various options for wood protection, starting from wood protection by design, to chemical wood preservation and wood modification methods. This should illustrate how important it is to combine an ecological understanding of the decay organisms, precise identification and innovative wood protection methods in order to achieve a long-term and thus resource-saving use of wood.
Key points
• Fungi and bacteria play a crucial role in the decomposition of timber wood.
• Traditional and advanced DNA-based methods for microbial identification are discussed.
• An overview of the various options for wood protection is provided.
... However, the cause of deterioration remained a mystery early on (50s, 60s, and well into the 70s) when LM was employed as the main imaging tool in examining waterlogged wood tissues. This is because the observed cell wall degradation pattern (such as the first LM image of cell wall degradation present in a foundation pole-see the review by Schmidt and Liese [30]) did not match any of the well-known fungal decay patterns, and at the time bacteria were not regarded as a microorganism that could cause wood decay. This led to the view that ancient waterlogged woods are mainly degraded by abiotic factors (for example, prolonged chemical hydrolysis). ...
... The micrograph taken during LM examination of a foundation pole (exposed to waterlogged environment) in 1950, published in the review paper by Schmidt and Liese in 1994 [30], displays features typical of wood degradation by erosion bacteria, although at the time it was not possible to ascribe the pattern to bacterial decay of wood, despite the presence of large bacterial populations. As mentioned earlier, determining the cause of deterioration of wooden artifacts uncovered from anoxic burial environments had to await application of high-resolution imaging tools (SEM, TEM) to unequivocally demonstrate that lignified wood tissues can be degraded by bacteria (and not only by fungi), as it became possible to unravel the intricate features associated with bacterial degradation of cell walls and close spatial relationship of bacteria with cell wall regions undergoing degradation. ...
Prehistoric and man-made ancient wooden artifacts are continually being uncovered from anoxic waterlogged burial environments where they are protected from highly destructive oxygen-dependent wood-degrading fungi. Microscopy has played a crucial role in understanding why such valuable buried objects remain well preserved for millennia. Suitable microscopy techniques have revealed that under anoxic burial conditions, wood is attacked mainly by erosion bacteria, which are well adapted to functioning in such environments, but the speed of wood degradation is extremely slow, in most cases resulting only in surface deterioration even after thousands of years of burial of wooden objects. The information emerging from microscopy studies is also proving crucial in more precise targeting of technology development to adequately conserve/restore the excavated precious wooden artifacts for human benefit.
... This was not achievable in earlier LM-based studies because of lack of clarity due to greater thickness of sections when compared to ultrathin TEM sections and inadequate resolution of LM. Inability to clearly resolve cell wall degradation patterns in decaying tissues at the LM level, although bacterial presence could be detected, led to the belief that bacteria could not degrade lignocellulosic cell walls [6,7,11,12]. ...
... The intricate architecture of tunnels provides the most important diagnostic feature. Many early bacterial wood degradation studies were based on LM that could not clearly resolve the pattern of tunneling degradation, although the presence of bacteria in decaying wood was detected [11,12]. However, use of TEM in subsequent studies provided a wealth of information on the pattern of cell wall degradation, revealing that degradation was caused by bacteria producing tunnels with a distinct and unique architecture. ...
Certain bacteria degrade wood by creating tunnels in cell walls. Transmission electron microscopy (TEM) has played a key role in understanding the intricate architecture of the tunnels produced within the cell wall and the process of cell wall degradation. The most prominent feature of tunnels is the presence of periodic crescent-shaped slime bands, which is the single most important diagnostic characteristic of bacterial tunneling-type cell wall degradation. The review presented covers the aspects relevant to understanding bacterial tunneling of wood cell walls, emphasizing the importance of the application of TEM in this area of research.
... Bacterial presence in decaying wood has long been recognised [81]. Early studies aimed to understand whether bacteria can degrade sound wood employed LM to examine decaying wood from natural environments and wooden constructions in service [82]. While bacterial presence in decaying wood was confirmed and decay features that did not resemble those described for wood-degrading fungi were observable, the progress in understanding whether bacteria could degrade lignified cell walls was hampered by the inability to obtain detailed views of such patterns due to the limited resolution of LM. ...
... Further progress made in determining chemical changes due to EB degradation of waterlogged archaeological woods concerns topochemical probing of the residual material and across the cell wall using UV spectrophotometry [99,100] and Raman confocal microscopy [101]. In the context of the above, it is worthy of note that an image (Figure 2 in [82]) from the first LM study of pine wood from a foundation pile undertaken by Walter Liese resembles the degradation pattern described as bacterial erosion. ...
This review provides information on the advances made leading to an understanding of the micromorphological patterns produced during microbial degradation of lignified cell walls of buried and waterlogged archaeological woods. This knowledge not only serves as an important diagnostic signature for identifying the type(s) of microbial attacks present in such woods but also aids in the development of targeted methods for more effective preservation/restoration of wooden objects of historical and cultural importance. In this review, an outline of the chemical and ultrastructural characteristics of wood cell walls is first presented, which serves as a base for understanding the relationship of these characteristics to microbial degradation of lignocellulosic cell walls. The micromorphological patterns of the three different types of microbial attacks—soft rot, bacterial tunnelling and bacterial erosion—reported to be present in waterlogged woods are described. Then, the relevance of understanding microbial decay patterns to the preservation of waterlogged archaeological wooden artifacts is discussed, with a final section proposing research areas for future exploration.
... Bacterial damage, however, was generally regarded to be minor because it is often slight and develops slowly compared to that of fungal attack (Henningsson 1988;Zabel and Morrell 1992;Clausen 1996). It was in the late 1990s where bacterial occurrence and its significance in wood decomposition was clearly recognized and demonstrated (Schmidt and Liese 1994;Singh and Wakeling 1996;Singh and Kim 1997) and suggested to be the main cause of destruction in archaeological waterlogged wood (Kim and Singh 1994;Kim et al. 1996;Singh and Kim 1997). In our days, however, it is a common knowledge that bacteria are the only confirmed microorganisms able to attack waterlogged archaeological wood in waterlogged anoxic sediments (Björdal et al. 2000;Klaassen 2008;Landy et al. 2008;Nilsson and Björdal 2008;Kretschmar et al. 2008;Singh 2012;Pedersen et al. 2012). ...
... Bacteria are thus divided into: (a) those decaying only pit membranes and non-lignified tissues and (b) true wood-degrading bacteria that degrade lignified cell walls (Blanchette et al. 1989;Blanchette 1995;Eaton and Hale 1993;Daniel 2003Daniel , 2014. The micromorphology types produced by true wood-degrading bacterial have been described as erosion, tunnelling and cavitation (Henningsson 1988;Nilsson and Daniel 1988;Blanchette et al. 1989;Eriksson et al. 1990;Blanchette et al. 1991;Singh and Butcher 1991;Eaton and Hale 1993;Singh and Kim 1997;Schmidt and Liese 1994;Blanchette 2000;Kim and Singh 2000;Landy et al. 2008;Rehbein et al. 2013). Cavitation bacterial attack, however, is rarely reported in recent years, more likely because it has not been possible to be reproduced and studied in laboratory conditions, such as tunnelling and erosion decay, and also because when this type is encountered, is often interpreted and described as erosion attack (Kim and Singh 2000). ...
Elements of evolution, taxonomy, morphology and physiology of wood deteriogens are discussed in this chapter, aiming to enlighten readers on their biology and enable the understanding of wood decay mechanisms. Wood deteriogens such as bacteria, archaea, fungi, insects and marine borers, utilizing wooden Cultural Heritage as a source of nutrients or as a physical substrate for their development, are presented. Bacteria and archaea are first addressed and their taxonomy, phylogenetic relationships and main morphological types are examined. Similarly, the ambiguous systematics and taxonomy of fungi are shown via a 9-phylum classification. Filamentous fungi features such as hyphae, mycelium, reproductive units and fruit bodies are defined along with their sexual and asexual life cycle. Based on the micromorphology and patterns of wood decay, bacteria are classified into erosion, tunnelling and cavitation bacteria, whereas the dikaryotic wood-decaying fungi are categorized into white-, soft- and brown-rot fungi. Marine wood borers, belonging to Mollusca and Crustacea are then recognized as major wood deteriogens encountered in marine ecosystems. Basics on their phylogeny, taxonomy morphological characters, physiology, feeding modes and life histories are presented. The molluscan bivalves attacking wooden Cultural Heritage are further mentioned and description of their body, reproduction modes, along with growth stages from the trochophore larva to the juvenile is made. Similarly, for wood-decaying crustacean orders, Amphipoda and Isopoda, their distribution, habitat, foraging behaviours and body features are discussed. Finally, insects, the most speciose group of animals of the planet is introduced and taxonomically classified. Their body segmentation is described and their life cycles from the egg to imago are explained, including the different modes of their post-embryonic development. Their feeding habits are also explicated for herbivorous, carnivorous and omnivores insects. General information on the biology and ecology of all wood-damaging orders are provided at last with special reference on wooden Cultural Heritage deteriogens, Coleoptera and Blattodea.
... Unlike fungi, these can adapt to a wide range of environmental conditions based on the availability of oxygen and nutrients (Blanchette, 2000). Lignin, cellulose, and hemicellulose are susceptible to bacterial attack as they represent an easy carbon resource for all those strains capable of decomposing these substances to obtain carbon (Schmidt and Liese, 1994). ...
Introduction
The evaluation of biological degradation of waterlogged archeological wood is crucial to choose the conservative and protective treatments to be applied to the wooden material. The waterlogged environmental conditions are characterized by oxygen scarcity, only allowing the growth of adapted microbes capable to degrade the organic wooden material, mainly erosion bacteria and soft-rot fungi. In this work, we characterized and evaluated the biodegradation state and the microbial communities of wooden fragments preserved in storage tanks. These were preserved by waterlogging within the Neolithic village “La Marmotta,” currently found under the Bracciano Lake (Lazio, Italy).
Methods
The waterlogged wood samples were first identified taxonomically with an optical microscope, also allowing an evaluation of their preservation state. The microbial community was then evaluated through the sequencing of Internal Transcribed Spacer sequences for fungi and 16S for bacteria with the Oxford Nanopore Technologies (ONT) MinION platform.
Results
The identified microbial community appears to be consistent with the waterlogged samples, as many bacteria attributable to the erosion of wood and ligninolytic fungi have been sequenced.
Discussion
The reported results highlight the first use of targeted metabarcoding by ONT applied to study the biodeterioration of waterlogged archeological wood.
... To obtain increasingly accurate information on the microbial communities involved in wood degradation, researchers have used classical cultivation methods and morphological examination to identify microbes (Rogers and Baecker 1991;Sterflinger 2010). However, the limitations inherent to these methods have yielded only a few candidates associated with the degradation of WAWs (Björdal 2012;Daniel 2014;Singh et al. 2016), such as species belonging to cocci and rod-shaped genera (Schmidt and Liese 1994). The accuracy of identification based on microbial morphology is also hampered by the different knowledge and perception of identification experts (Rogers and Baecker 1991;Sterflinger 2010). ...
The Jingtoushan Site (8300–7800 BP), located in Ningbo City, Zhejiang Province, is of great value for the in-depth understanding of China’s prehistoric coastal culture. At this site, numerous valuable wooden relics showing past human civilization have been discovered. Multiple approaches were taken, including wood anatomy and physicochemical analyses, to assess the preservation state of waterlogged archaeological woods (WAWs), while using high-throughput sequencing (HTS) to explore their microbial diversity and composition as well as that of the surrounding soil. The secondary walls of WAWs showed to be severely degraded, whereas the compound middle layer and cell corner were well preserved. Bacteria were the main microorganisms causing the biodegradation of WAWs, and 85.6% of the phyla was also found in the surrounding soil environment. Specifically, Arcobacter, Flavobacterium, Hyphomicrobium, Pseudomonas and Sphingomonas, bacteria retrieved by HTS in high abundance, were inferred to be potentially associated with the biodegradation of WAWs at the Jingtoushan Site. Meanwhile, it is hypothesized that lignin in the wooden artefacts still buried and unexcavated at the Site might be at risk of further degradation, although it may be better preserved than the cellulose and hemicellulose.
... Hence wood species such as poplar, willow and white fir are more susceptible to bacterial degradation and that too this decay happens mostly in the heart wood portion. Bacterial wood decay may not be very prominent, but in combination with fungal wood decay, it can cause fast degradation of wood (Kim & Singh, 1996;Schemidt & Liese, 1994;Singh & Wakeling, 1997). ...
Wood is an ancient material used in the development of human civilization. It is the first material used by the human kind for its protection and survival that further came into use as material for shelter preparation and food preparation, as fuel wood. Since then the wood has become an integral part of day-to-day life of mankind. This renewable and recyclable material however forms material of food, shelter and reproduction for many other organisms too. In this chapter we have discussed about the joint action of major organisms, which are dependent on wood for their survival and also the environmental factors in the process of wood degradation. Such degradation of wood and wooden products results in enormous economic loss, and it has a negative impact on the present era of global warming, as carbon locked in the wood is released in the process of degradation. Consequently, the possibility of mitigating wood degradation is also discussed.KeywordsWood degradationFungusBacteriaInsectsMarine borersWood protection
... Details of EB degradation process and decay patterns on a cellular level are described elsewhere (Singh et al., 1990;Singh and Butcher 1991;Kim et al., 1996;Björdal et al., 2000). The identity of EB are still unknown although both traditional culturing (Schmidt et al., 1987;Schmidt and Liese 1994) and advanced molecular techniques have been used (Landy et al., 2008). DNA profile from both archaeological wood and foundation piles indicates a highly diverse microbiota with a huge number of both known and unknown bacterial species belonging to different classes, families, and genera (Helms et al., 2004;Landy et al., 2008;Palla et al., 2013;Antonelli et al., 2020). ...
Nine wooden foundation piles of spruce and pine supporting historic buildings in the old town of Gothenburg, Sweden, were examined for fungal and bacterial degradation. The aim was to assess the type and degree of decay of the pile heads and correlate variations to the local environment, time in service and the wood quality. Soil and water samples were measured in the field for basic hydrogeological analyses, and pH, redox, O2 and groundwater level. The piles showed strong similarities in decay. Detailed light microscopy examination revealed that solely erosion bacteria caused degradation; both in outermost soft layers of the sapwood and further inwards. Most severe decay was present in the outermost layers, 1–3 cm, thereafter decay generally decreased and stopped at varying depths. Most piles had sound interior wood tissue, but a few were superficially to moderately degraded throughout. Some piles showed pronounced variation in degree of decay at the north respectively south side of the stem. This might be related to local water flow directions in the soil. In two piles, minor decay by white rot and soft rot were observed. Soft rot attacks were concluded to be of older date, most likely related to the time of construction, whereas white rot either infected the wood during an aerobic period; e.g. extreme drainage of unknown date, or alternatively the attack developed already in the living tree before felling. Despite that all pile heads (except one) were exposed below groundwater level and mainly in compact clay soil with low redox values, it was not possible to correlate any specific environmental parameter from soil and pore water analyses to the observed decay rates. Diameter of the pile and time in ground were the only two factors clearly correlated to the long-term performance of the piles in this specific urban environment.
This review focuses on the pivotal role microscopy has played in diagnosing the type(s) of microbial attacks present in waterlogged ancient wooden objects, and to understand the nature and extent of deterioration of such objects. The microscopic journey began with the application of light microscopy (LM) to examine the deterioration of waterlogged woods, notably foundation piles supporting historic buildings, progressing into the use of high-resolution imaging tools (SEM and TEM) and techniques. Although bacteria were implicated in the deterioration of foundation piles, confirmation that bacteria can indeed degrade wood in its native state came when decaying wood from natural environments was examined using electron microscopy, particularly TEM, which enabled bacterial association with cell wall regions undergoing degradation to be clearly resolved. The information base has been a catalyst, stimulating numerous studies in the past three decades or so to understand the nature of microbial degradation of waterlogged archaeological wood more precisely, combining LM, SEM, and TEM with high-resolution chemical analytical methods, including chemical microscopy. The emerging information is aiding targeted developments towards a more effective conservation of ancient wooden objects as they begin to be uncovered from burial and waterlogging environments.
Typescript. Thesis (M.S.)--University of Wisconsin--Madison, 1960. Includes bibliographical references (leaves 83-87).
Bacteria have long been known to be associated with wood in service 1. In recent years the effect of bacteria on wood kept in water has been intensively studied and bacteria have been shown to increase the permeability of the sapwood of many timber species by destroying the pit membranes.2,3. Studies on the bacteria regularly isolated from wood in ground contact 4, 5, 6 by many authors have been conspicuously lacking.